My new fish died after tank cycling. My betta has fin rot. What to do?
Updated On September 23rd, 2025
Hi I just bought fishes and most of them died. They probably died due to the tank was in the process of being cycled. I had 9 fishes and only have 2 fishes left which are femal bettas. I Have one betta that was doing fine but then weeks later she has only one pectoral fin and is sitting on top of the water it moves only if the other betta bothers it. The fins look like it has black sticks. She still has her tail fins. She is probably dead by the time I get back from work. If not what can I do
4 Answers
Most Helpful Answer
Published on February 24th, 2020
I recommend to start with having the water tested. Many times this is offered by the pet store. If all the fish have passed away, the culprit is most often poor water quality, a disease or the tank not being properly maintained for the species of fish. I do not recommend to get more fish until you know the water conditions are correct and that you know the environment (temperature...etc) is appropriate for the species of fish you want to have. I hope this helps.
1Pet Parents found this answer helpful
Related Answers from Veterinarians
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Published on February 25th, 2020
This is likely fin rot. The tips are not always blackened with rot, they can simply appear ragged. The condition typically resolves by maintaining pristine water quality as you have seen previously. Perform regular partial water changes. Use only conditioned water that is temperature matched to prevent stress or shock. Bettas are tropical fish and do best between 78 F and 80 F. If possible, turn down filter flow to the lowest setting. Bettas prefer slow moving water.
3Pet Parents found this answer helpful
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Published on November 17th, 2017
The black patches may be due to elevated ammonia levels. This may cause "burns" on scales. Perform a partial water change immediately. Use only aged or conditioned water that is temperature matched (78 F to 80 F) to prevent further stress or shock. Poor water quality can lead to fin rot or infection. This can be remedied, in most cases, by maintaining water quality. You can add a bit of plain aquarium salt (NOT table salt) to aid healing and reduce stress. One teaspoon of salt per gallon of water is recommended. Dissolve it completely in a cup of tank water then gently pour it into the tank.
1Pet Parents found this answer helpful
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Published on June 24th, 2017
Make sure you have a male instead of a female Betta. Determining sex can be tricky in young Bettas until about two months of age. You can post a picture in Jake's profile or attach an image to a new question. If he is indeed a male with short fins, check for signs of infection such as fin rots. Signs include ragged fins, clamped find or lethargy. Water quality plays a role in overall health, so make sure the tank or bowl had adequate filtration, chemistry and oxygenation. If necessary, there are medications that can be purchased to treat bacterial or fungal infections that contribute to fin rot. Check the aquarium section in your local Petco for broad spectrum medications. Follow label directions carefully.
1Pet Parents found this answer helpful
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