i have a ten gallon tank, 2 dwarf gouramis, 1 otto and 6 longfin zebra danios. I have noticed the smallest zebras fins look like they have been nipped on they do somimes chase eachother but i didn't think zebras would do that.
Hello
It's pretty crowded in there, and crowding can lead to nipping and agression. Danios can and do nip each other, it could also be your gouramis; they're slow, territorial fish, and the speedy danios might be driving them nuts with all that activity. The only sure way to tell who's biting who is to watch them for a while and catch someone in the act.
I agree... you're a bit crowded... but danios nip/chase each other, that's just the way they are. Keep an eye out, as Blinky suggests, to see who is actually doing the nipping.