Bettas Keep Dying?

[juhason]

So I have a 55 gallon fish tank with 2 angelfish, 2 kribs, 3 diamond and 3 candy cane tetras, and 4 julli cories. At first I tried added 5 female bettas, and all of them hung out at the top in the corners of the tank, not moving at all until they all slowly died off. Now I'm trying a male betta and he is doing the same thing (but he hasn't died yet.) It doesn't make any sense to me as my water chemistry is fine and all my other fish are happy and healthy, living in there for months. I also know bettas to be extremely hardy, more hardy than most other fish I've ever kept. Does anyone know what could be happening? 

 

[bluesword23516]

The angel fish or kribensis could easily kill them off. As far as the other fish they might be pestering him too. I would take out the betta. 

 

[Wildbetta]

Honestly your stocking does not seem like the best to work with bettas.  Cichlids and bettas normally do not do well together unfortunately.  What it sounds like it happening is that the bettas are highly stressed to the point of death which can happen when bettas are added to communities.
 
I recommend working a bit with your current stocking.  Adding 3 more of each type of tetra to bring their numbers both to 6 and adding 2 more cories to bring their number up to 6 as well since all of these fish are shoaling fish that need groups of at least 6 of their own species to be comfortable.