New betta fish sick: fuzzy fungus, lying on bottom. How to save him?
Updated On September 23rd, 2025
Pet's info: Fish | Unknown - Fish | Male
Hello! I purchased a male koi betta from a Petco two days ago. He is currently living in a two gallon filtered aquarium. Yesterday I noticed him laying on the floor of the aquarium, but I assumed he was just sleeping. Today when I woke up he was covered in a sort of fuzzy substance, which I assume to be fungus, and still laying on the floor of the aquarium. Sometimes he will get up and swim around. I want to do something to prevent him from dying, but I don't know what to do. Please help!
3 Answers
Most Helpful Answer
Published on June 16th, 2017
If you set up your tank and added Cola the same day, it is likely you are having water chemistry issues in addition to a fungal infection. Tanks should be set up and run for about 4 weeks before adding fish. This allows the tank to cycle. This means beneficial bacteria will populate the filter and substrate. It is important because they rid the tank of toxins such as ammomnia and nitrites. Since he is in the tanlk already, you can use a quick start product to jump start the nitrogen cycle. You can purchase this at the pet store. You will also need an antifungal medication. Follow label directions carefully. Make sure water temp is between 78 and 82 F and use a low flow filter to prevent a strong current. Partial water changes (no more than 30%) may be necessary to reduce ammonia and nitrite levels until the tank has cycled. Used aged or conditioned water that is temperature matched.
1Pet Parents found this answer helpful
Related Answers from Veterinarians
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Published on July 25th, 2018
It could be some fin rot and fungus growth. The foundation for treatment and recovery is pristine water. You can use a home test kit or submit a water sample to confirm proper chemistry. Most pet stores will do this for free or for a small fee. Aim for 0 ppm ammonia, 0 ppm nitrites and 20 ppm or less nitrates. Perform a partial water change if indicated. Use aged or conditioned water that is temperature matched to prevent further stress or shock. Do this every few days to maintain water quality. To treat the fungal infection, you'll need a product such as Fungus Cure (API) or LifeGuard All In One (Tetra) . You can find them in the Aquarium section of the local Petco. Follow label directions and remove the carbon filter insert during treatment. Water changes and medication should resolve the infection in a week or two. The fins should slowly heal up afterwards. Perform regular testing and partial water changes to keep the tank clean. Remove any uneaten food to prevent fouling the water. Feed a high quality, high protein pelleted diet. Hikari makes several types. You can find them at Petco as well.
1Pet Parents found this answer helpful
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Published on November 18th, 2018
He has to get used to his home. Moving him to a new tank can be stressful. Fish can handle not eating for up to two weeks, so there is no big worry yet, Make sure his water temperature is adequately warm. If the water is too cold, he will not be hungry. Check water chemistry using a home test kit or by submitting a water sample for testing. Aim for 0 ppm ammonia and nitrites with a 40ppm or less nitrate level. Perform partial water changes to stabilize chemistry and maintain water quality. Use only aged or conditioned water that is temperature matched to prevent stress or shock. A bit of aquarium salt (NOT table or Epsom salt) can be used as a general tonic to reduce stress, treat minor infection and aid in any recovery. Dissolve 1 teaspoon of salt per gallon of water in a cup of tank water and gently pour it into the tank.
1Pet Parents found this answer helpful
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