My betta fish has a growing lump on its side. How can I treat it?

Maintain pristine water quality via filtration and regular partial water changes. This is the cornerstone for treatment and recovery. Plain aquarium salt (NOT table or Epsom salt) can be used as a general tonic to reduce stress, improve gill function, treat minor infection and aid in recovery. Dissolve 1 teaspoon of salt per gallon of water in a cup or two of tank water and gently pour it into the tank. Treat for 14 days then reassess the condition. If necessary, a broad spectrum antibiotic can be used concurrently. Find one in the aquarium section of the local Petco. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.

Without an image or exam, it is difficult to say with any certainty what the lump may be. Infection or injury would be likely culprits. If he has anything sharp in his bowl, remove it. Check the water quality and chemistry as poor water quality can predispose him to infection. Use a home test kit or submit 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 improve water quality. Use only aged or conditioned water that is temperature matched to prevent stress or shock. Bettas do best between 78 F and 80 F. Change no more than 30% total volume at one time. You can try using plain aquarium salt (NOT table or Epsom salt) as a general tonic. It can treat minor infection and helps aid in recovery. Dissolve 1 teaspoon of salt per gallon of water in a cup of tank water and gently pour it into the tank. Treat for 10-14 days then reassess his condition. Perform water changes afterwards to reduce salinity. Do not use salt for more than 14 days in a row. If there is no change, a broad spectrum antibiotic can be found in the Aquarium section of the local Petco. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.

Thanks for reaching out about Spike and including a photo. It is difficult to visualized the lump on the picture but if water quality is pristine, a veterinary visit might be in order to assess. Bumps/lumps can be parasites, infections, enlarged internal organs and more. Monitor appetite. Containers of food should be re-purchased every -23 months as vitamin C degrades quickly and fish has a nutritional requirement for vitamin C. If not a new fish (owned for several months or more), unlikely to be parasitic problem. Good luck.

Thanks for reaching out about Cosmo. Dermal tumors are fairly common in betta fish. Some are benign, others malignant. A biopsy would be needed to determine. Malignant tumors tend to grow faster. If a tumor, nothing at home can be done, but a veterinarian would likely be able to remove. Good luck.

Maintain pristine water quality via filtration and regular partial water changes. Use only conditioned water that is temperature matched to prevent further stress or shock. Bettas do best between 78 F and 80 F. You can try an "all in one" product, such as Lifeguard by Tetra, to treat the condition. Find it in the local Petco or online. Follow label directions carefully and remove the carbon filter insert if indicated. https://www.petco.com/shop/en/petcostore/product/tetra-lifeguard-all-in-one-freshwater-aquarium-treatment

Thanks for reaching out about Neo and including photos. He does appear very ill, don't think age is the reason as two is not old. Age is not a disease, something else is a problem. With sinking to the bottom, a swim bladder infection is possible. Offering peas as a high fiber food works with over-inflation, not this. Systemic antibiotics are needed and therefore a veterinary visit. Water quality needs to be measured, just not changed. Good luck.

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.