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Why did my betta die after a water change? Is my other betta at risk?

Updated On September 23rd, 2025

Pet's info: Fish | Unknown - Fish | Male | unneutered | 0 lbs

Trying to figure out why my female betta died this morning. I had a male in the tank with her (with a divider). She was acting fine and eating. I did do a water change but I only but in “bottled betta water”. I also added a heater but I unplugged it when it got to 82 degrees. The male is fine. Do I need to do a water change or anything for him or should he be fine? I got them both a week ago at the same time

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1 Answer

Most Helpful Answer

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Answered By Angel Alvarado, LVT

Licensed Veterinary Technician

Published on September 27th, 2018

Drop the water temperature to 80 F. Bettas do best between 78 F and 80 F. The higher temp likely did not cause her death, but warm water holds less oxygen than cooler water. She may have been ill or old. She does appear bloated in the image. It may have been dropsy or other infection. Monitor water chemistry using a liquid test kit. They are more accurate than the strips. Tou can also submit a water sample for testing. The local Petco may do this for free or for a small fee. Aim for 0 ppm ammonia and nitrites with nitrates at 20 ppm or less. Try to keep the pH as close to 7 as possible. Bettas can tolerate acidic water, but changes should be gradual to allow time for acclimation.

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