My goldfish has a growth on its head. Should I be worried or is it normal?

Hi and thanks for your request and pictures. This tumor like lesion could be due to a lymphocystis. This is a virus (herpes), mostly seen in goldfish, which can cause these type of cauliflowers mass-like lesions. Of course to be confirmed, this should be sampled and or removed completely. Unfortunately these masses can grow much bigger that the one showed in the pics and can become infected. A clinical examination at your local veterinarian is essential to confirm these clinical suspicions and treat appropriately. Hope this answer was helpful, but please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further. If this answer was helpful please let us know, this will be used to improve our service!

It could be "pop eye". This can be caused by infection or trauma (aggression or from tank furniture). Treatment will include medication and maintaining pristine water quality. Goldfish produce a larger than average bio load (wastes) which can quickly overwhelm a tank and filter. Ideally, one goldfish should have 20 gallons of water and 10 additional gallons should be added per extra fish. The filter should be rated for at least twice the volume of the tank. Check water chemistry using a home test kit or by submitting a water sample for testing. Most pet stores will do this for free or for a small fee. Aim for 0 ppm ammonia and nitrites with a nitrate level of 20 ppm or less. Partial water changes can be done to stabilize chemistry and maintain water quality. Use only aged or conditioned water that is temperature matched to prevent stress or shock. Goldfish are cold water fish and do best between 65F and 72F. A broad spectrum antibiotic can be found in the Aquarium section of the local Petco. These include erythromycin, tetracycline or kanamycin. Brands include Kanaplex, Maracyn , FishMox or FishCillin. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.

It may be a bacterial infection or trauma. Monitor for bullying since you have other fish. Most minor infections can be managed or resolved by maintaining pristine water quality. A bit of plain aquarium salt (NOT table or Epsom salt) can be used as a general tonic to aid in recovery, reduce stress and improve gill function. Dissolve 1 tablespoon per 5 gallons of water in a cup or two of tank water and gently pour it into the tank. Treat for 10-14 days then reassess the condition. If the condition is unchanged, consider a broad spectrum antibiotic. You can find one in the aquarium section of the local Petco. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.

A 5 gallon tank is insufficient for goldfish. They produce a larger than normal bio-load (wastes) that can quickly overwhelm a small tank. Ideally, one goldfish should be in a 20 gallon tank with an extra 10 gallons added per additional goldfish. The filter should be rated for at least twice the volume of the tank. They are likely succumbing to ammonia and/or nitrite toxicity. If you test the water, it is likely both parameters will be dangerously high. Perform a 50% water change. Use only conditioned water that is temperature matched to prevent further stress or shock. Goldfish are cold water fish and do best between 65 F and 72 F. Plain aquarium salt, NOT table or Epsom salt, can be used to reduce stress, improve gill function and aid in recovery. Dissolve 1 teaspoon per gallon in a cup or two of tank water and gently pour it into the tank. Treat for no more than 14 days then perform a partial water change to decrease salinity. A 5 gallon tank would be appropriate for one male Betta or a small school of Neons (3-5).

Looking at the photos, I agree that it doesn't look like the typical fungal infection. Generally you see multiple lesions and they tend to be fuzzy in appearance. I'm not sure what that is on the fin but it may be benign. I would recommend to call the pet store and tell them what you are seeing. Check to see if any of the other fish have become ill. Abnormalities on the fins can be fungal, bacterial or parasitic. There's also a change of a defect or injury. If the area is not really changing and your fish is acting normal, you may just monitor it. I hope this helps!

Goldfish are susceptible to fibroma tumors (benign) and sarcoma cancers (malignant). I cannot tell you what they are exactly just by looking at the photos. As long as they do not bother the fish (interfere with movement, bleed nor cause discomfort), most people leave them alone.

If it is fuzzy, it is likely fungal. You can try with a commercial antifungal medication such as API Fungal Cure, methylene blue or Pimafix/Melafix. These can be purchased online or in the aquarium section of most pet stores. Read package directions carefully and remove the carbon insert from the filter before treatment if indicated. Plain aquarium salt (NOT table salt) can be used in conjunction with one of the above treatments to aid healing. Dissolve up to one tablespoon per gallon of water into the tank. Fungal infections can take up to two weeks to resolve with treatment. Maintain proper water parameters (0 ppm ammonia/nitrites, 40ppm or less nitrates and temp of 65 F to 72 F). If possible, remove the affected fish yo a hospital tank during treatment.