Dying Betta Fish

[FemaleBettaLove]

I have a 30 gallon tank with a betta sorority with community fish and all of the sudden, one by one, the bettas are falling ill and dying. First, the sick fish will be at the bottom of the tank more and then eventually it will stay at the bottom with its face towards the ground and tail in the air. They will occasionally come up for air. The bettas that have acted like this die within a day or two. I suspect high nitrates (ammonia and nitrite are 0) so i have done 2 50% water changes so far. On the api test kit, it is difficult for me to tell the colors of the higher end of the nitrate scale, but i know it is at least 40+ ppm. Also, the fish look like their bellies are big, but I just fed them and they are greedy with food.

I currently have the remaining bettas in their quarantine cups. I am new to diagnosing and treating sick fish and am unsure what to do. I added a sprinkle of Epsom salt and erythromyacin to try and cover everything I can think of.

Finally, with all of this happening, I have had a few neon tetras die. In the tank there are also ember tetras, whitecloud minnows, pygmy cories, one glass catfish (his buddy died), a panda garra, albino pleco, and a few amano shrimp.

Any help in diagnosing and treating my fish would be greatly appreciated.

 

[Autumnsky]

How long has the tank been set up? Have you ever tested over weeks/months and know you had a stable tank?

It certainly sounds like the possibility of disease. Do you see any parasites in gills or eyes, anal vent, or on the body?

https://www.aquariumadvice.com/fish-disease-index-for-diagnosis-and-treatment/

 

[FemaleBettaLove]

The tank has been set up for about 3 months. I know it is cycled and was consistently testing nitrate levels. I didn't see any outward signs of illness on the Bettas. They would just become lethargic and spend more and more time towards the bottom of the tank until they passed away. As of now, 2 Bettas remain and I have them separated. I originally had 4 healthy ones remaining and they were in quarantine for about 4 days with no signs of anything, so I put them back in (hoping 4 Bettas were enough to keep aggression down) and the next morning 2 were dead. It is possible the last 2 were killed overnight because I didn't see any signs of sickness while in quarantine. I haven't seen anything wrong since the last death, and all of the remaining fish are fine as of now.

I am working on keeping nitrates low. They were high because I was on a trip and was unable to do water changes. Everything is back on schedule now and I am planning on adding a pothos plant to try and consume the nitrates. My tank is already planted.

 

[Autumnsky]

Have you noticed what their poop look like, possibly internal parasites.

And check the Bettas you have left. Maybe one is a male. I had a group of young females, but, one ended up being a male and killed a few girls. He was a younger one so I couldn't tell. But after he was removed they weren't dying.

The part about being lethargic may be a separate thing, or the stress of being hunted if you do have a male could leave their weakened bodies susceptible to illness, like internal parasites or other things.