zebra danios

[bubbles]

I've got a tank with 13 fish (all compatible tropical freshwater) and this includes 2 standard zebra danios and 2 veiltail zebra danios.

However, the veiltails (who are slightly bigger) are constantly chasing the other 2 danios around the tank and now I think the 2 normal danios are suffering as they do not seem to be swimming properly and always slowly hover around the bottom of the tank. They both appear to be eating though.

Do you think the 2 veiltails are stressing my other danios out and is it possible that it could kill them? Is the answer to get more normal zebra danios?

Any advice from anyone is much appreciated.
Thank you.

[wetmanNY]

Constant chasing is the Danio lifestyle. The stress may come from gill parasites. Are they respiring faster than normal?

Many patent medicines containing formalin and malachite green together eliminate ectoparasites.

[beviking]

I've always (o.k., for 2+ yrs) had zebra danios. Long-finned and regular, gold colored too. Mixed and matched them. No matter what combo I had, eventually, they claim a territory and chase others out. In the lfs, they always seem to be playfully chasing each other, which they do in my tank also, but they seem to get set in keeping others away from a staked area. I tried adding more and they just started chasing the other fish more often. Thought I had a "bad" batch and bought new ones. I'm down to 3 long finned ones now, soon to be 2 b/c one is constantly driving other fish (all fish) out of one corner and I suspect that one is the reason for the loss of anothers' eye. This is only my experience with them. I don't recall any being harassed to the extent of hanging at the bottom however. I would look into other possible reasons for that behavior as wetman suggested. Good luck!

[bubbles]

Thanks for that - at least I know its common for danios to chase each other around the tank. Perhaps they have become terrortorial, as suggested.

I'm hoping get a much larger tank soon, so perhaps some extra space is needed.