Fin rot or nipping?
I recently put 5 tetra in with my male beta in a 10 gallon tank. I have had them in the past together, but these are new fish, so I know my beta's personality can be different. I had these guys for about 2 weeks. When I first got the tetra there was a lot of nipping between them, but nothing more than establishing a pecking order. Since then there hasn't been any problems. My beta doesn't appear to be bothered by them. He claimed his territory and the tetra stay away.
Yesterday I couldn't find one of my tetra (I have a ghost shrimp who may have added to the disappence) and this evening I found another one dead in my tank. My water levels are natural but I am a concerned because I noticed one of my tetras fins. I included a picture, any thoughts? I plan to do a water change tomorrow, do i need to get medicine?