My betta, a beautiful pinkish, silverish, purplish (he was sold as a "half-moon betta) has a tendency of staying on the bottom of the tank. I've read some articles about swim bladder disorder and how too much freeze dried food can cause it, but I haven't even fed him any. Yet. And also constipation can cause him to stay on the bottom. He sometimes does not eat his food, but usually does. Should I feed him 1/4 of a pea? What should I do?