My goldfish has redness around their top fin, is holding their top fin, and has had a crooked tail for a week. What should I do?

This could be a bacterial or fungal infection. If there are other fish in the tank, trauma cannot be ruled out. if there are other fish, ideally Tiny should be removed to a quarantine or hospital tank for treatment. If not, you can treat Tiny in the main tank. First, confirm adequate water quality. You can use a home test kit or submit a water sample for testing. The local Petco may offer water testing for free or for a small fee. Aim for an absence (0ppm) of ammonia and nitrites with nitrates at 20ppm or less. perform partial water changes, no more than 30% total volume at a time, using conditioned and temperature matched water. Goldfish are cold water fish that do best between 68 and 74 F. The filter should be rated for at least twice the volume of the tank. Plain aquarium salt (NOT table salt) can be used to reduce stress, treat minor infection and aid in recovery. Dissolve 1 tablespoon of salt per 5 gallons in a cup or two of two of tank water and gently pour it in. Treat for 10-14 days then perform water changes to reduce salinity. Only treat the amount of water being replaced. More often than not, pristine water quality will allow recovery of minor infections or trauma. If necessary, you can use a broad spectrum antibiotic or all in one product, such as LifeGuard (Tetra) or All In One Remedy (Marineland), to treat the tank. You can find these products in the Aquarium section of the local Petco or online. Follow label directions carefully and remove the carbon filter insert during treatment.

The bowl should have frequent partial water changes to maintain water quality it there isn't a filter in place. Use only aged or conditioned water that is temperature matched to prevent further stress or shock. Goldfish do best in water temperatures between 65 F and 72 F. The swelling and redness could be a mass, infection or, more serious, dropsy. An Epsom salt bath (NOT table salt or aquarium salt) may help with any swelling or fluid retention. Dissolve one tablespoon of epsom salt into one gallon of tank water. Allow a 15-30 minute swim before returning him to the main tank. Consider also a broad spectrum antibiotic to treat any infection, primary or secondary. You can find one in the aquarium section of your local Petco or fish store. Read and follow package directions carefully.