The guy who sold me my black widow BTAs told me they might fight with the RBTAs, but I figured since they are the same species, I didn’t take it too seriously and just kept them appart. The black widow BTAs have been in the tank a couple weeks and have been deflating like spaghetti every other day or so then recovering in a few hours. The RBTAs have been perfectly healthy ever since I put them in a few months ago. However yesterday they all seemed a little off, all partially deflated at once. The water parameters were pristine, there is no stray voltage and two fish died, a maroon clown and flame hawk that were perfectly healthy the day before. Two others are recovering in a QT.
I originally suspected velvet. After reading the velvet sticky, I'm not convinced that’s what’s happening here. The flame angel fully recovered in less than a day in QT and the maroon clown looks like it's only having equilibrium problems at this point, possibly neurological damage from acute toxicity. More importantly, there were never any white spots, even on the two fish that died.
Here’s the question, can two types of BTAs engage in chemical warfare given that they are the same species, and if so, can it harm the fish in a small tank?
Here's the thread I started in the fish disease section.
https://www.reef2reef.com/threads/unknown-toxicity-in-tank.784719/