It seemed to have some sort of fin disease, so I thought I'd separate the betta from the rest of the fish by putting it in a cup (the idea being that I could change the water more often and keep it safe from the other fish.) He jumped out of the cup, and over the desk. It was still alive when I found it on the floor, but when I returned it to the tank I noticed one of his fins isn't moving. The little fish are picking at his tail too, which has been a bit bloody and tattered since I came in to work today (which is why I put it in the cup to begin with). Poor thing--what should I do?