I have a 29 gallon tank subdivided into 5 partitions, with a single male betta in 3 of the partitions, a paradise fish in one, and one partition empty. The tank is relatively new, but cloned in part from my mature 55 gallon tank. The only water parameter that is questionable is the pH, which is a bit higher than I would like at 7.6. There are two power filters - one pretty gentle and small, and one large and noisy with high flow. The betta partitions are the 3 partitions where the filters do not flow directly - in fact, there is only minimal current in the betta partitions.
When I set this up, one of my bettas started acting stressed immediately - I figured it was the shock of being moved from his old tank to the new tank, or maybe an injury during the move. He held on for several weeks, but finally died two days ago.
About 3 days ago, one of the other bettas started acting stressed out as well, and the 3rd betta has now followed suit. The paradise fish seems to be doing well.
Other than the obvious stress, I can see no other signs of illness - they simply lay on the bottom, rising to the surface every once in a while to breathe.
Just to be sure they weren't stressing at the sight of each other, I erected some opaque plastic between the partitions, but that seemed to make no difference. (Besides, they had been able to see each other when I had them in separate tanks.)
I'm beginning to suspect that they are stressed out by the continual sound of the large filter, which is several orders of magnitude noisier than the gentle flow from their previous residences.
Does this seem like a reasonable possibility? Would it be a good idea to shut off the big noisy filter until I can arrange something that will be less stressful to these guys? (I can run out tonight and get something if necessary.)