I woke up this morning to feed my fish and I saw one of my ADFs floating on the surface! I thought he was dead, and I touched his leg just to make sure, and he swam away! That was a big relief...He also let out a little bit of air and then sank to mid-tank, but then swam back up to the top for more air (quite tiredly). Once he gulped more air he continued to float on the surface. What's wrong? What can I do? I'll test water parameters after class at 12 and post them. I hope he's okay :-/