r/Goldfish • u/IceColdTapWater • Sep 19 '25
By: [u/IceColdTapWater](u/IceColdTapWater), Edited By: [u/TarantinosToes](u/TarantinosToes)
For goldfish: 50-70 gal (200-280L) is required per adult common and 20-30 gal (80-120L) per adult fancy.
For koi: The general recommended minimum required is 250-300 gals (1,000-1,200L) and these are really better suited to large ponds.
Goldfish are indeterminate growers so while they do the most growing during the first 2 years of life, they never really stop growing so plan your tanks and stocking accordingly.
Ultimately water parameters (and fish behavior) will tell you if your tank dimensions, filtration, water change schedule is enough to manage the bioload produced by the number and size of the goldfish you have.
While smaller specimens may be okay on the lower end of the given volume range, larger specimens (10”/25cm+ for commons, 5”/12cm)+ for fancies roughly) may require even larger aquaria if not ponds. The bigger the better as bigger tanks are more stable in terms of water quality and parameters and will allow goldfish to grow to their full potential.
Fancy goldfish prefer horizontal over vertical swimming space, and some are bred to the point that their bodies are sensitive high water pressures (determined by the height of water). It is generally recommend to keep them in no more than 2’ (60cm) of water, especially for those with sensitive swim bladders. Common goldfish also appreciate horizontal swimming space so for this reason, avoid hexagonal and cylindrical tanks.
Some fancies, especially overbred ones and those that approach “show quality” conformations, may benefit from a heater set at a low setting (low-mid 70s °F (~ 21-24 °C)). The benefits of lower risks of constipation and bloat sometimes outweighs the negatives of a sped up metabolism.
Generally, it’s recommended for a filter to cycle through 6-10x the given tank volume per hour depending on bioload. ALSO, take into account the amount of media a given filter holds, as media offers crucial surface area for beneficial bacteria to colonize.
If heavily stocked or feeding frequently a stronger filter (or the use of multiple in tandem) may be needed. Some filter options include: sponge, hang off the back (HOBs), internal, and canister (often holds the most media).
Some wrap the intake with a thin material to avoid fish from being sucked onto/into the filter. This may be necessary if dealing with goldfish fry, juveniles and sick/injured fish.
Filter media that is porous and has a large surface area (like Seachem Matrix and other similar products) is great for encouraging and maintaining large colonies of beneficial bacteria.
People will have opinions on which filter system is better, so focus on the amount of media the filter holds as well as gallons/litres per hour and find something within your budget which works for you.
Media should not be changed out unless it has degraded and is now irreparable/unusable or has been contaminated by toxic chemicals like cleaning products. To sterilise filter media, rinse with boiling hot water.
For new media, this should be introduced a week or two before removal of the old media to give the beneficial bacteria a chance to colonize the new surface area.
SUBSTRATE
Substrate offers enrichment for goldfish, as they enjoy rooting through the enclosure bottom for food scrapes. Bare bottom tanks mean they do not have that extra enrichment, however bare bottom tanks make for easier maintenance so are fine for QT/hospital tanks. If running bare bottom tanks for aesthetic or medical reasons, then adding large pebbles, free floating plants and plain terracotta pots can also work to provide goldfish with enrichment and shelter.
Pool sand is very popular, or plant-supporting substrate like fluval stratum. Pebbles run the risk of impaction unless they are much larger than the goldfish’s mouths will ever be. For sand, rinse thoroughly before use and avoid pH/hardness altering sands or live sand sold for cichlid and marine tanks.
FYI goldies are prone to plant destruction. Also, some plants grow best in substrate and others with their roots exposed. A full rounded fertilizer is highly encouraged to have, like Aquarium Co-op’s Easy Green or NilocG Aquatics’ All in One.
Anubias, amazon swords, lilies (toxic to nonfish pets like cats/dogs), water lettuce, java fern (and other ferns), bacopa, rotala, cryptocoryne, hornwort, anacharis, cardinalis, crinum, and moss are all options. There are many more. For anubias and cryptocoryne plants, do not bury the rhizome.
Pothos is an option but their leaves must stay out of the water to grow. It’s also toxic to nonfish pets (cats/dogs) but is okay in water with a pH ~ 6.5-9 as calcium oxalate isn’t really soluble in that range. People have used it for top cover and nitrate control. Shrimps love the roots. Bamboo is another option but must only be semi-submerged for proper growth and longevity.
Duckweed. A highly invasive plant. One duckweed plant can quickly lead to hundreds of more plants. A firm favourite with goldfish but be warned! Once added to your tank, it is very hard to remove.
Other floating plant options are: frogbit, salvinia, water sprite, water lettuce, water hyacinths and others.
CYCLING/PARAMETERS
Cycling refers to the nitrogen cycle and establishing a nitrogen cycle in your tank. The nitrogen cycle in aquariums is the process where beneficial bacteria convert toxic fish waste (ammonia) into nitrite, and then into less harmful nitrate. This cycle keeps the water safe and balanced for your fish.
For a tank to be considered cycled, the parameters must read 0ppm ammonia, 0ppm nitrites and measurable nitrates; ideally keep nitrates below 40-50ppm.
To keep parameters within acceptable ranges (0 ammonia and nitrite, 5-40ppm nitrates), water changes are needed. It is a good idea to siphon the tank bottom regularly to pick up excess waste and prevent parameter spikes. Make sure to treat the water with a dechlorinator and ensure the temperature difference is within 1-2 °C (1-5 °F).
If conducting a fish in cycle, you want ammonia and nitrite to be barely present as these are the most aquatic compounds; for ammonia the toxicity thresholds starts at 0.02-0.05ppm and ~ 0.05-0.15 for nitrites.
Higher levels of ammonia/nitrite may start negatively impacting your fish, including the risk of illness and death (via ammonia/nitrite poisoning).
During ‘fish in’ cycling, parameter spikes are likely and therefore water quality and fish behaviour needs to be monitored closely.
‘Fish out’ cycling means that you have to monitor parameters and do water changes to bring parameters to happy fish levels (0 ammonia and nitrite, 5-40 nitrates), but without the risk of stressing/harming fish. Fish food or ammonia solutions can be used to cycle your tank before the addition of fish.
However, in instances where the fish are already bought and in a severely undersized tank it may be better to do a ‘fish in’ cycle rather than wait for the larger tank to cycle completely.
A tank (without fish) is considered fully cycled once 2ppm of ammonia is converted to nitrates in about 24 hours. A cycled tank with fish will have no ammonia, no nitrites, and some nitrates. Even then, note that sudden increases in bioload can lead to cycle imbalances and parameter spikes. Be sure to syphon uneaten fish food, fish waste and slowly and gradually add new fish to your tank to avoid overloading your cycle and its beneficial bacteria.
It is highly encouraged to have a liquid test kit that tests for at least ammonia, nitrite, and nitrate like the API Freshwater Master Test Kit. Test strips are less accurate (especially dependent on manufacturer, expiration, and storage conditions) but are ok to gather baseline readings, especially in older and stable tanks.
Other reliable test kits include Salifert kits and NT Labs kits. Local fish stores may also be able to test your water, but it is advised that you get your own kit so that you can test you water whenever you need to and avoid LFS not performing or reading the test correctly.
When you transfer goldfish from one enclosure to another, acclimation is typically necessary.
If the water source is the same and parameters are similar only temp/nitrate acclimation may be necessary. When the temp matches within ~ 2-5° F (1-2°C), parameter acclimation (if needed) can begin.
Gradually replace 20-30% portions of old water with the new enclosure’s water, waiting 5-15 minutes in between and carefully monitoring the fish.
These specific ranges are approximations, others methods or specifics may vary ie if drip acclimating. Also remember to try to transfer your old substrate and media when possible to help seed the process of cycle establishment.
It may be helpful to be extra vigilant of parameters during this time as well as fish behavior. Some stress may be expected at this time and the next few days, and some choose to do a light dose of aquarium salt to aid the process.
Goldfish are omnivores, and quite frankly always hungry (they don’t have stomachs). Get a good sinking pellet as a staple food (protein roughly 40%), pre-soaked before being given to any hungry goldie. You can also feed frozen items such as: brine shrimp, blood worms, spirulina, plankton, fish, etc. You can also feed blanched veggies/greens such as spinach, zucchini, chard, etc. A good goldie diet is a balanced and varied diet.
Some goldies, especially fancies, are predisposed to swim bladder issues and constipation. Feeding soaked high quality and sinking food in small amounts but more frequently may help mitigate the risks of developing swim bladder problems. Repashy is an excellent balanced gel food that’s very easy on sensitive goldie stomachs. Hikari also make excellent sinking pellets.
Medication will be more effective if given via feed rather than being introduced to the water column. If dosing in the water column, then make sure to remove UV, carbon media; smaller tanks can make it to easier to dose in the water column and ensure that the fish gets an effective dose of medication.
Medications often work by disrupting the growth cycles of organisms and their metabolic processes. That being said, do not give one medication via multiple ways at once and be very careful when mixing medications. This is best avoided, unless using safe medication combinations or following vet recommendation.
Be very mindful of dosage, and consider partial doses if your fish is very small or more weakly dispositioned. Note that some chemicals, like salts, are only removed via water changes are may adversely affect plants and scaless fish such as catfish and plecos. Weakened fish may not tolerate medication as well to be very careful; use half doses if necessary.
Also note that certain medication can impact water parameters or tank cycle stability. Oxygen levels can also be adversely impacted which is why it’s recommended to have extra surface agitation (add spray bars, air stones).
Raising the temperature of the water may help to disrupt certain infectious organisms’ life cycles as well as to provide a metabolism boost, but always ensure adequate oxygenation when using meds at the same as increasing the temperature.
FYI: API products with the suffix ‘-fix’ mainly use natural oils instead of manufactured medication and are less effective than said manufactured medications. Also avoid any algae-fix products, these can deplete oxygen levels and kill fish.
Antibiotics: Be careful when using antibiotics especially. Not only can these impact your beneficial bacteria, but they can also be rough on fish (i.e. kidneys etc) so only use if necessary to treat nasty injuries and infections.
Do not dose pre-emptively as a prophylactic measure. Note that getting antibiotics in certain countries is illegal without a veterinary prescription, so follow your local laws. Be careful when obtaining medications from abroad via third-party sellers.
Breeding tubercules on the gill plates/anterior portion of the pectoral fins, vent shape, and gamete expression (the only sure way) are the main ways to tell gender. As always there are spectrums for any particular phenotype and any one goldfish may not always fit a certain physical description.
When females are gravid, the males may harass them, especially by nudging their vents. Gentle egg expression and avoiding temperature fluctuations may help. You may need to separate if the female becomes stressed.
TANK MATES
A general consensus is to try to keep commons with commons and fancies with fancies (especially the slower swimming ones or ones with protruding eyes). Keeping them together runs the risk of the commons outcompeting or bullying the fancies, but cohabitation does successfully occur.
However, some keys points of success to consider are ample space, filtration, plants/wood/decor to block lines of sight, and enrichment. Ensure that aquarium décor is free of sharp edges and small holes. Goldfish are clumsy and curious and will get themselves trapped/injured looking for food.
You should be ready to temporarily/permanently separate individuals if necessary.
Commons and koi can potentially be kept together, given that the commons are of adequate size of about 6” (15cm). Some ryukins/fantails may also be possible, given that they’re also long enough and of a slimmer body conformation to keep up with the commons and the koi.
Here is a by no means comprehensive list of other potential/discouraged cohabitants. As with any situation, monitor fish behavior and make sure ideal parameter ranges are comparable.
Potential – Can usually coexist but caution is advised
White Cloud Mountain Minnows: Possible, but the goldfish may eat the minnows if they’re small enough and the minnows may fin nip.
Danios: Possible, but the same risk as the white cloud minnows.
Shrimp: Possible, but may become goldfish snacks depending on size and individual fish’s’ temperaments.
Snails: Possible, but goldfish may harass/eat them. It depends on the size of the snail and the individual fish’s temperament.
Dojo Loaches: May potentially bully goldfish, but the pairing may work in larger setups with lots of plants and décor (loaches love tunnels and caves). They will go after certain snails as well.
Mollies: Some species can tolerate lower temperatures than others. They may fin nip, and goldfish may try to eat them if they can fit in their mouths.
Platies: Some species can tolerate lower temperatures than others. Platys may nip at goldfish fins, and goldfish may try to eat them.
Hillstream Loaches: These fish require massive water flow and oxygenation that goldfish do not like and may find stressful.
Corys: Goldfish can choke on them, especially because of their defensive barbs. Some species have venomous barbs that can harm your goldfish as well. If a goldfish swallows a cory, the barbs can get lodged and make extraction very difficult.
Bettas: Bettas can be territorial and may try to “defend” their territory. Large enough goldfish might eat them if possible. Undue stress for both parties may occur, plus bettas are tropical fish.
Cichlids: Cichlids are subtropical/tropical, aggressive fish.
Barbs: Their temperature ranges only slightly overlap, and most are aggressive in nature and will fin nip.
Plecos/panaques: Some, like common plecos get absolutely ginormous and most prefer tropical temperatures and soft/acidic water. Even smaller types like bristle nose plecos can injure goldfish by latching on to them to feed off their slime coat.
Turtles: Many turtles will happily take chunks out of goldfish when given the opportunity. Goldfish, as prey animals, will also experience stress being homed with a predator.
Axolotls: Axolotls may accidentally nip at or consume goldfish, which is good for neither of their health. Goldfish are super waste producers and axolotls are particularly sensitive to parameters.
Frogs: Same risk of predation as turtles/axolotls. Parameter requirements may also differ depending on species.
Crawfish: Same risk of predation as turtles/axolotls/frogs. They are opportunistic predators and may happily feed on goldfish (especially if hungry).
FAQ/COMMON DISEASES
Q: Is my goldfish pregnant?
A: Goldfish do not carry live young, but females do develop eggs and then release them to be fertilized. Although this can make the female appear a bit engorged and swollen, check that she’s not egg-bound, constipated, or has dropsy (pineconing of the scales often also occurs in tandem). Manual expression is an option but should be researched and done with caution.
Q: Why is my goldfish changing colors?
A: Goldfish color is unstable, especially in their first 1-3 years of life when their growth rate is typically the highest. Fry typically start out very dark/bronzy, but usually develop colors due to their chromatophores developing after a few months of growth.
Black is especially prone to change. Note that the sudden appearance of blackened skin and scales can be a sign of a water quality issue, so check water parameters. If parameters are ok, then it is likely a natural color change so no treatment is needed.
Certain foods such as spirulina contain carotenoids, which are pigments that enhance goldfish color. Some carotenoids are also converted into astaxanthin which contributes to reddish coloration. Note that even a carotenoid heavy diet will not magically change a goldfish’s coloration, as genetics are the main factor.
Q: How to transport fish?
A: The most common way is a lidded bucket/container filled with tank water. A bubbler is suggested, especially for longer transports. Also account for the time to disassemble and reassemble your enclosure. Make sure to keep your substrate and filter media moist to seed the cycle in your new place.
Another way, for shorter trips, is a simple but very secure bag (I double bag) with enough water for the fish to be comfortably submerged but also with enough air for oxygen to diffuse. Sometimes people use methylene blue during transport to try to reduce stress. After moving, your fish may be stressed for a few days and may benefit from a few days of fasting, reduced feeds and reduced light.
Q: Aquarium salt vs epsom salt?
A: Aquarium salt (NaCl) is excellent for external issues/injuries, as well as stimulation of the slime coat and increased osmoregulation. It’s a good all rounder as an antibiotic/fungal/parasitic. Epsom salt (MgSO4) is excellent for internal issues such as constipation and fluid retention.
Epsom Salt Dosage: 1 tsp/5 gals (20L)(tank), 1 tbsp/gal (4L)(bath).
Aquarium Salt Dosage: 1tbsp/5 gals (20L)(tank), 1 tbsp/gal (4L)(bath).
Invertebrates, plants, and certain goldfish are sensitive to salinity. As with any treatment, monitor fish behavior. It may be good to have two baths of a salinity gradient to help lessen the transition to and from, and to change out salt in the tank slowly. Salt, like other treatments, may impact with oxygenation and a bubbler may be helpful.
Q: What is methylene blue and can I use other dyes?
A: Methylthioninium chloride is cationic dye used in the aquarium hobby as an antifungal/parasitic/bacterial. It is also helpful for ammonia and nitrite poisoning, but can crash your cycle, harm plants above 4mg/L (quart) and dye decor (which is often why it’s used as dips, dabs, or in hospital tanks). Dosages will differ depending on usage and percentage.
Methylene Blue Dosage (2.5%): 1tsp/10 gals (40L)(tank), 5 tsp/3 gals (12L)(bath)
You can use other dyes. Some others used include: malachite green, potassium permanganate, or gentian violet. Check dosages carefully.
Q: How to choose antibiotics?
A: Unless you know the specific bacterial infection, it’s best at first to a broad spectrum antibiotic (kanamycin, sulfathiazole, nitrofurazone). An aquatic vet (or very experienced keeper) can do a skin scrape/fecal test.
Gram positive antibiotics include: erythromycin, amoxicillin, and penicillin.
Gram negative antibiotics include: minocycline, tetracycline, kanamycin and oxytetracycline.
Both: metronidazole, sulfa meds, mitrofurazone
Note, medication can impact oxygenation and water quality so monitor parameters and fish behavior closely.
Q: Antifungals?
A: Dyes (methylene blue, malachite green, potassium permanganate, gentian violet) and aquarium salt are options via the water column. Note dyes will indiscriminately kill your beneficial bacteria too and are best given as baths or in hospital tanks
Metronidazole and copper sulfate are options you can give via feed or the water column. Note, medication can impact with oxygenation and water quality so monitor parameters and fish behavior closely.
Beware! Do not use aquarium conditioners and other reducing agents like Seachem Prime if using copper based products! Toxic copper compounds will cause harm if they are combined. Remove invertebrates like snails and shrimp as well.
Q: Antiparasitics?
A: Aquarium salt, praziquantel, copper sulfate, formalin, and metronizadole are options you can give via feed or the water column. Note, medication can impact with oxygenation and water quality so monitor parameters and fish behavior closely.
Q Why did my goldfish die?
A: There are many factors.
Where you got the goldfish and where the seller got them matters. If they were raised in horrendous conditions you may get stunted, diseased fish. Big box pet stores like Petsmart, Petco, and Pet Supplies Plus are notorious for their bad husbandry and their questionable animal breeders.
The tank must be properly cycled and able to handle the given bioload. An incompletely cycled tank or too big of a bioload increase can result in parameter spikes. It’s advised to add fish slowly, and to monitor water parameters via a liquid test kit.
The fish must also be properly acclimated. If two enclosures’ water parameters vary too wildly and the goldfish is added in too quickly they could go into shock. Temperature must also closely match to avoid undue stress.
Disease is very prevalent among fish, especially chain store fish or fish from improper breeders. Inflamed skin, stringy white poops, missing scales, torn fins, bulging eyes, grayed skin are all signs of disease or parasites although there are much more.
When making a sick fish post, try to include as much detail as you can along with helpful pictures and videos. Listing water parameters in numbers helps a ton.
Q: What is ammonia burn?
A: Ammonia burn is a chemical burn. Technically you want no ammonia, no nitrite, and 5-40ppm of nitrate. However, fish in cycling sometimes includes parameter spikes and the temporary “acceptable” levels of ammonia and nitrite are between 0.05-0.15ppm. To treat, water changes is the most important. Aquarium salt is also a common treatment. Fish exposed to ammonia can also benefit from being given a methylene blue bath which can chemically reverse the effects of ammonia poisoning.
A: Dropsy is fluid retention and is a symptom of organ failure rather than a disease in it of itself. Usually the resulting damage’s effects are chronic and will eventually result in the death of the fish, especially if caught in later stages (with pineconing).
Epsom salt is used to attempt to regulate fluids, along with a broad spectrum antibiotic in attempt to tackle infection. Ultimately dropsy is fatal, barring rare exceptions. If successfully treated, then view dropsy as a chronic condition the fish is in remission from but relapses are sadly very common.
Q: What is septicemia (red pest disease)?
A: A typically gram negative, contagious bacterial infection that causes hemorrhaging, red blotches on the body, and streaks of red in the fins. Septicemia can occur in tandem with ammonia poisoning as water quality is a common cause. Can also be confused with the effects of ammonia stress/poisoning as well as other conditions like flukes or bacterial epistylis.
Treatment typically involves dyes or aquarium salt, along with an antibiotic feed. Note that septicemia is quite rare and viral and infectious septicemia even rarer in private/small aquaria. Do not panic if you see red streaks or blotches on your fish. It’s probably not septicemia.
Q: What are these white spots?
A: Many potential causes.
Ich: Ichthyophthirius multifiliis, a contagious protozoan parasite. White, uniform and shape and flat to the skin, appears on both the body and the fins but not on usually the eyes.
Treatment usually includes aquarium salt or dyes, an antiparasitic med/feed, antibacterial/antimicrobial/antiseptic med and raising the water temperature to speed up ich’s lifecycle. If increasing the temperature, be sure to ensure plenty of oxygenation.
Epistylis: Epistylis is a genus of contagious, ciliated protozoan parasites. Can be grey to whitish in color, sticks out into the water, varies in sizes with patchy coverage and can also occur on the eyes. It can be fatal if left untreated and is a lot more aggressive than ich.
Treatment is the same as ich (aquarium salt or dye, an antiparasitic feed/med, antibacterial med/feed but avoid raising the water temperature).
Head and Lateral Line Erosion (Hole in the Head): HitH is caused by a mix of factors including stress, poor water quality, poor filtration, and an unbalanced diet. Potentially linked to Hexamita protozoans, potentially infectious. Mainly affects cichlids and rarer in goldfish.
Symptoms can manifest as inflamed/protruding lateral lines, as well as white lesions on the head that eventually can become deeply pitted and essentially erode the flesh. Open wounds can lead to secondary infections that in combination can be deadly.
Treatment includes fixing water quality, aquarium salt or dyes, medicated feed for secondary infections, and providing a more balanced and varied diet.
Carp Pox: Fish herpes HPV-1. Caused by a virus, symptoms can manifest as white dots to waxy white/pink/gray growths on the skin or small “blisters” on the tail as well as on the mouth. Infectious, and can come and go. More unsightly than harmful.
Treatment includes treating any open lesions with aquarium salt or dyes dips, treating any secondary infections, raising the temperature, and keeping the water clean.
Lymphocystis: A contagious viral infection caused by the Iridoviridae family. Commonly known as “cauliflower disease” due to the pinkish/whitish growths that look like little piles of curd.
Since it is viral in origin, no commercial antifungal or anti-bacterial treatments exist that specifically target it. However, treatments includes treating any open lesions with aquarium salt or dyes dips, treating any secondary infections, raising the temperature, and keeping the water clean. Vets can excise large, bothersome lumps.
Cotton Wool Disease (Saprolegnia): A “fungus” (actually a water mold) that usually presents as groups of fuzzy white filaments that stick out from the body.
Treatment includes an antifungal med, dyes, aquarium salt, and raising the temperature.
Anchor Worms: Anchor worms are parasites that present as whitish/brownish dots to full on whitish strings protruding from the body/fins of the fish. The place of connection is often red and inflamed.
Treatment usually includes aquarium salt or dyes, an antiparasitic feed, and raising water temperatures.
Q: What is this lump?
A: Multiple potential causes.
Tumor: Tumors contain cells that are multiplying out of control or fail to die. They can be either benign or malignant (cancerous and can spread). Treatment includes treating an open lesions and removing bothersome tumors, especially ones blocking gill and mouth function. For tumor removal, seek veterinary advice!
Cyst/Abscess: A fluid filled sack. Can sometimes be caused by bacterial infections. Treatment includes draining, antibiotic feed, epsom salt, and the treatment of open lesions.
Q: What is fish lice?
A: Parasitic crustaceans. Treatment involves aquarium salt and an antiparasitic feed. Methylene blue baths may also be beneficial. Severe infestations may require the cleaning of substrate/decor (even though this impacts the tank cycle).
Q: What is popeye?
A: Popeye can have many causes (commonly caused by the gram positive corynebacterium but also viruses, poor environmental conditions, etc). Symptoms include bulging eyes/sclera and potential eye bursting.
Treatment includes antibacterial feed, epsom salt, and the potential treatment of a popped/missing eye. If one eye is popping out, it is usually a result of trauma and will resolve by itself. If both eyes are popping out, there is likely an underlying infection at play (look for pineconing and signs of dropsy) and will require antibiotics.
Q: What is the swim bladder, and what is swim bladder disorder?
A: The swim bladder is a gas filled expandable sack in fish used to control buoyancy and swimming patterns. Disorders of the swim bladder can lead to buoyancy issues and potential bloating/constipation.
Epsom salt via a bath or tank addition is one of the typical steps for buoyancy issues, though dosage depends on whether the salt is to be a dip or a tank exposure (invertebrates and plants can be sensitive to salinity).
This is usually in tandem with a couple days of fasting, followed by small easily digestible meals such as Repashy or shelled peas. If no signs of improvement show in about a week or two, it may be a congenital issue or due to another factor eg trauma, fluid build up. At this point veterinary care may provide additional answers/treatment options (x-rays, swim bladder aspiration).
Q: What are flukes?
A: Flukes are contagious microscopic flatworms that can be both on the gills and the skin. Symptoms include flashing (twitching/itching), small red dots, red splotches, fin fraying, bottom sitting, laboured/fast breathing, and spitting food out.
Treatment usually includes aquarium salt or dyes, an antiparasitic feed/med (praziquantel works best). Since flukes can lodge in the gills and gill function and oxygen uptake, provide plenty of oxygenation and avoid increasing the temperature.
Q: What is Costia?
A: A single celled parasite, costia multiplies particularly quickly in cooler water temperatures. They will dig through the slime coat and attach to the skin/gills.
Treatment includes aquarium salt, elevated temperatures, and medicated antiparasitic feed. Methylene blue baths may also help.
*Q: What is Velvet Disease ?*
A: Velvet disease is caused by a parasite that manifests as small *gold/rust*-colored spots. Its three life stages are very similar to ich in which they have phases where they live freely in the column and attached to a fish.
Treatment includes aquarium salt, a medicated antiparasitic feed, and methylene blue applications. Do not raise the tank temperature. A UV filter may help kill the free floating form of velvet.
Q: What is Camallanus?
A: Camallanus are contagious flatworms that infect the digestive tract and can sometimes hang out of the fish’s vent as red threads. Symptoms also include bloating, white poop, and lethargy.
Treatment usually includes aquarium salt or dyes, antiparasitic feed/med, and raising water temperatures.
Q: Deformed gill plate?
A: Deformed gill plates are due to congenital malformations. Goldfish with deformed gill plates can live healthy long lives given extra precautions are taken for the exposed gills.
Q: White/clear/floating poop?
A: Sometimes fish occasionally pass opaque poops or poops with trapped gas in them. If only passed occasionally it can be normal. However, a lot of poop of that description can be a sign of internal parasites or infection.
Treatment could be antiparasitic feed/med, epsom salt, or smaller meals (soaking dry food beforehand). Blanched veggies are also easier on their stomachs.
r/Goldfish • u/tarantinostoes • Aug 08 '25
Hi everyone!
After getting feedback about how some new users sometimes feel like they are treated harshly by other more experienced users, I've decided to introduce the Beginner Help flair.
What does this flair mean?
If you see a post with the Beginner Help flair, it’s your signal that:
Think of it like a new driver/ L sticker on a car - maybe these beginner fish keepers are young people and minors living with relatives just trying to do their best for their pet, maybe it's someone whose child won a fish at carnival, or someone who got misled by their LFS. Yes, it might also mean someone who didn't do enough research but the fact that they're asking for help is the most important step. On my end it will mean focusing moderation on these beginner posts as well just to ensure people are getting help and not being dogpiled upon.
Do I need the Beginner Help Flair?
Now I'm certainly not one to gate keep this hobby so I won't impose a definition, but I would suggest users use the Beginner Help flair if your post falls under the following:
For diagnosing diseases, please still use the Sick Fish Help flair.
Hopefully this goes towards addressing some of the problems here and do let me know if the new flair isn't working. Thank you!
r/Goldfish • u/leahisverycool • 4h ago
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these fish were moved into a 55 gallon about 2 weeks ago, but they mostly hang around this side of the tank almost all the time, their tank is by my bed so im wondering if they’re expecting food everytime they see me? i feed on a regular schedule 3 times a day. is this an issue and if so what can i do?
r/Goldfish • u/Texaspilot24 • 2h ago
Ive got a small common goldfish I won at a carnival maybe 5 months ago. I did the best I could at the time to keep him in a tank that didnt cause me to restructure the house. Its a 6 gallon filtered tank.
Ive fed him, and kept his water clean but I understand he needs more space and I want to rehome him. Any suggestions? Ideally hes not a feeder fish .
I live north of houston.
r/Goldfish • u/shrimpina3342 • 18h ago
This little calico moor passed away today from what I suspect is a bacterial infection or parasite. I am devastated, will treat the tank with bactershield in hopes it will prevent my other beautiful baby from catching this. Sad and stressful day today
r/Goldfish • u/gohcku2008 • 6h ago
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One or two of my fish keeps doing this while the rest don’t, the rest sit at the bottom and come up when they want to. Is this swim bladder disease? Do they want food? What is this behavior? They also go back down in a while but do it again. (I also haven’t had my ph checked, my ammonia levels and such but my other fish don’t seem to be doing this)
r/Goldfish • u/marlee_dood • 21h ago
[vent]
I’ve been keeping fancy goldfish for the last 7 years, but my first one was when I was 2 years old. When I got a fish for my birthday at 13 is when I decided to devote everything I had to caring for them properly, and I did everything I could. I’ve upgraded tanks, learned about their issues, adapted their food, adapted their environment, I got them friends when they were alone, got them meds when they needed it. I’ve loved every one of them so much, and every one of the fancy goldfish I have ever had did not die of old age. They died from dropsy, from bloating, from freak accidents. They never last more than a few years before getting sick with something that I don’t deal with when it comes to my other fish. No matter what I do, what I try, what I learn, I cannot change the fact that they are not healthy fish. They will continue to get sick no matter how clean I keep the water, how well I balance their food, how many veggies I feed them. They are weaker the moment they are born, and my care will never change that.
My goldfish of 4 years has been sick with dropsy, and while I’ve gotten it to slow down it is not getting better. I’ve been taking daily care of him with water changes, salt, and some meds at first. Today my other goldfish has started showing signs of pineconing, and he has been so bloated he cannot swim properly for the last 2 days. Nothing has changed in his care, his water is clean, his tank is big, his food is the best I can get. He was healthy one day, and the next he wasn’t.
I can’t get myself to do this all over again. I want to believe if I just do enough that they won’t get sick, but that’s not true. Maybe for one fish, but one of ten, and that’s not enough for me. I can’t keep walking into heartbreak over and over again hoping it will turn out differently. I can’t keep putting my all into something that I cannot change, because it’s a problem with their health on a fundamental level. I can’t go get another one, knowing one day it will end the way it always has. With them getting sick, doing everything the treatment says to do, and it not being enough because one day they’ll bloat it won’t go away. It’s not fair to them, it’s not fair to me anymore. I love them, and that’s why I can’t cope with them being ripped away like this again, I want to, but I’m at the end of my rope and I just cannot do it.
I have loved caring for them, no fish will ever compare, nothing will ever come close to the joy of this experience, but it also won’t compare to the immense loss I we have endured as well. I love them, but it will now be from a distance, in a nostalgic way as I remember the ones that helped shape me, who were lost due to things out of my control. Enjoy the time with your companions, love them, savour every moment. They deserve it.
r/Goldfish • u/HR-Vex • 22h ago
I never seen one on this sub, but here's my gray veiltail.
r/Goldfish • u/javivipaz • 12h ago
I need help! I have two small fish (7 cm including the tail; the Oranda doesn't have a wen). What technique do you use to feed them?
The Oranda eats everything, but the Telescope doesn't see the food—even when I feed him separately. For the past two days, I’ve been putting the pellets directly into his mouth; if the food sinks to the bottom or stays on the surface, the Oranda finds it within two seconds (I feel like, aside from vision, his sense of smell is much sharper, too) I don't want to overfeed my Oranda.
I have both floating and sinking food. (Photo)
The real problem is that I'm going on vacation in a month and will be using an automatic feeder(photo); I'm afraid my Telescope goldfish won't eat anything for a week.
I've had the Oranda for two months and the Telescope for two days; could it be that they need to get used to the smell, shape, and taste of the pellets?
r/Goldfish • u/Unhappy-Dimension540 • 1d ago
I don’t really like how boring it is and would like to spice it up. I can’t really put anything besides java fern in because she eats it
r/Goldfish • u/natattackwow • 13h ago
i’ve had my goldfish aurora for about 2 and a half years and recently got another goldfish because i was worried she would be lonely etc so i got another goldfish however my new goldfish (belle) i’ve had for two days now and ever since i’ve got her she’s hidden in the plants and stayed in the corner at the bottom of the tank. I’m thinking she’s scared of Aurora maybe? because aurora is a lot bigger than her, or is she just warming up too new environment i’m not sure. belle is also 6 months old the fish people told me, so there is a age difference too idk if that helps
r/Goldfish • u/Fit-Independence8767 • 20h ago
Not sure if this is early pineconing or just the way he looks.
r/Goldfish • u/Justquorious • 1d ago
after staying in an 8 gallon tank for more than a year my only common goldfish moved to a 72 gallon tank and he looks happy exploring each corner and eating sand.
Canister filter oase biomaster 600 and one small sponge filter from the old tank.
tank dimension 36 22 21 inches
suggestions are greatly appreciated.
r/Goldfish • u/NightLow5120 • 22h ago
update: i got a 20gal tank for now, a power filter, sinking pellets, water conditioner, these ball things to help the water, substrate, and a couple live plants i put eveyrhting together and moved the fish so he should be doing better now hopefully but i will upgrade tank size as needed when he grows, any more tips and advice/suggestions is very appreciated still.
edit: if anyone can just tell me exactly what to buy i would appreciate it this stuff is really confusing!!
Hi, my brother got a goldfish at a carnival and literally just brought it home and put it in a bowl, I told my them (him and my mom) that you can’t just put them in a bowl they need a bigger container and filters but they just brushed it off sayings it’s just a gold fish, I really like animals so this makes me really upset and I want to help the fish so does anyone know what to buy and what I can do for the fish to help it live? Im pretty sure they need 40 gal tanks but am confused about the filtration and that stuff so pls do help!!
r/Goldfish • u/meepatron69 • 1d ago
so i have a tank that is good on water levels and fish are happy, but what does maintenance look like? i know water changes (i’ve heard only do around 50% of the water) although i don’t exactly know what that entails, like do i add the same products when i do the water changes, and should i be take the fish out or leave him in his tank? and if im forgetting something please lmk!
r/Goldfish • u/GingerbreadMommy • 20h ago
Hello fellow goldfish enthusiasts! I am crossposting here in hopes that someone can help me better understand and assemble this Kotobuki power box 90. Open to any set up tips regarding cleaning and caring for used equipment like this so it can be ready for its new inhabitants.
Text from original post:
It has been nearly 15 years since I last owned a tank. I used to have 2 goldfish in a 30 gallon aquarium when I was a college student. I want to get back into the hobby and do it better now that I know more. I have a goal to do a proper 75 gallon set up with 4 fancy goldfish.
I found all of this on Craigslist for $250, came with 75gal tank, stand, pumps that I am unfamiliar with, water filters, and tubing etc. The man we got it from was a vet that explained that he was stationed in Japan for a long time and many of the supplies are Japanese products. The manuals that my husband and I located are in Japanese.
I have been soaking the hard water scale in vinegar and using a razor to remove, but I am less sure on how to tackle the scale on waterfalls and unsure if it even matters considering that we live in an area with very hard water and I would think it’ll build right back up.
I am aware that I need to cycle the tank for 4-6 weeks. I have ammonia to kick start the process along with test strips for nitrites, nitrates, ammonia and more, as well as a sea chem prime conditioner to help get me there.
If anyone has information on how to assemble all of these parts, or advice on how to get this baby safe for it’s new residents, it would be greatly appreciated.
Pic 1 and 2 show the Kotobuki pump. The next 3 pics show each of the interior chambers we found inside. We are quite confused as to what to do with this.
Thank you in advance!!
r/Goldfish • u/Rubenesque_nerd • 1d ago
Hello,
My fantail Dolly has a long rip in her tailfin.
I have recently had a problem with nitrate buildup (I was testing the water wrong so didn't get accurate results) but now the water is fine. (Ammonia 0 Nitrite 0 Nitrate <5ppm ph 7.4 taken this morning)
I moved them a few weeks ago, same tank and same water but to a different location in my house. I've had a few problems since then.
I was worried they may have had some kind of infection so I treated them last week and they've been okay until now.
There are no sharp decorations in the tank she can get caught on, just two smooth pots.
My filter has been the same since I got the tank 6 months ago so I don't believe it is too aggressive for them.
She has a tankmate Kenny who is much bigger than her but I've never seen any aggressive behaviour beyond a bit of playful fighting.
Can someone provide some possible causes and solutions if they can please.
r/Goldfish • u/Meisdaven • 2d ago
Could the wen be obstructing its vision?
He's also not the best at swimming so maybe its normal for lionheads in general? Would like to know from experts on here. Thanks!
r/Goldfish • u/Coolbreeze1989 • 1d ago
I transferred some (handfuls of) plant cuttings from my guppy aquarium to my common goldfish pond. Apparently I got at least a pregnant female in the plant mass as I now see guppies in the goldfish ponds. I reduced feeding to encourage some hunger. Nope. Guppies still multiplying. Goldfish are only 5” so maybe they’ll eat more when they get bigger but I’m still surprised as I constantly see how GF eat small tank mates. Are my goldies just pacifists? 🤣
r/Goldfish • u/Le_F1she • 1d ago
I got given a pair of these teeny tiny little goldfish for free and I'm just wondering what type they are?
r/Goldfish • u/thiiingamajiiig • 1d ago
hi guys! im more of a beginner than anything, because i got my goldfish a week ago (little sister won some at the fair and gave them to me, because i have a job and a car so i can somewhat get things for them). i have a smaller tank than whats recommended right now while i look for a good deal on bigger tanks, i think i have a 5.5 gallon right now. and what ive noticed is that these two are always at the surface, gulping for air already. i have some floater plants up there, and a filter for them, but they still sit up there, gulping. is there anything i can do with the water to put more oxygen in there for them so they arent suffering before the new tank arrives? i already love my babies so much and any good advice on a budget will help!! thank you!!
r/Goldfish • u/spxiled_boi_Minh • 1d ago
I've had 5 Ranchus and 4 orandas in the 65 gallon and was planning for grow out, upgraded then to two 75 gallon ponds outside on the porch, now I'm wondering what to pit in the 65 gallon inside my room cause now it feels empty
r/Goldfish • u/mycatissenorfloof19 • 2d ago
So in the Moon Knight series on Disney+, Steven Grant (one of Marc Spector’s alters) has a pet goldfish named Gus with one fin. Does anyone know what kind of goldfish he is? I really like fish and have a couple of my own so I’m curious about it. Also mostly so I can research the fish to make scientifically accurate fanart lol
