Vet Q & AWhy are my fish floating up and have red rashes? Are they sick?
Check water quality using a home test kit if you have one. If not, bring a water sample to the local pet or fish store. Either may test water for free or for a nominal fee. Confirm 0 ppm (parts per million) ammonia and nitrites. Nitrates should be 40 ppm or less. Partial water changes using aged or conditioned water can be done to improve water quality. Many times poor water quality can lead to stress or infection. The symptoms described may point to swim bladder disease. This can be caused by infection, constipation, stress or parasites. The red rash may indicate infection.
Fast your fish for 3 days then offer bits of cooked, shelled green peas until they are swimming and defecating normally. A product such as Maracyn or Kanaplex may treat infection. You can purchase either (or generic antibiotics such as tetracycline amoxicillin or erythromycin) in the aquarium section of the local pet or fish store. Follow label directions carefully and remove the carbon filter insert if indicated during treatment.
Make sure water temperature is between 78 F and 80 F, this is the optimal range for bettas.
Updated on September 24th, 2025
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