injured fish!

I've had a guppy and a cremesicle Lyretail Molly for quite some time, and the guppy has always enjoyed playfully chasing the molly around the tank. This morning, however, I guess he was hungry, as he decided to nip at the Molly until the poor guy had several red spots on him. As soon as I fed...

One morning i woke up and couldn't find my very active Buenos Aires tetra. So i started looking around for it. When I found it, it was in the corner of my tank and had a good size hole in tits side. I immediately separated it from the rest of the tank and put in a separate tank. I am wondering...