I've had my betta for a couple months now and a few days ago I decided to add a couple of cory catfish to his tank. I only bought two because I wanted to see if he was okay with them before I added more (I know they like to be in big groups). I have a ten gallon tank with sand, some plastic plants and one live plant. A couple weeks after I got my betta, I noticed his fins weren't as pretty as when I first got him. But he seemed happy and was always swimming so I thought he was fine. Now his fins seem a little frayed. After putting the cory catfish in the tank, my betta seems to stay closer to the bottom and is always resting on plants. He chased the cories a little in the beginning but now seems fine with them. But he still seems depressed. Or maybe he has fin damage? I've done some research on fin rot and I don't think it's that. Anybody have any ideas as to what's wrong with him? Or am I just freaking out over nothing?