I woke today to feed my azureus dart and he wasn't moving, he just kinda crawls around the tank, then stops. He did this for the 1st day when I got him, I don't know what is wrong with him, he was fine yesterday, he ate and swam and was hopping around just fine. Now he just lays there. The temperature in the tank did a drop a few degrees, is the issue? I have a black heat lamp on the tank to try to raise the temperature. idk what I will do if he dies.... please help