So my axolotl has been sitting in one corner of the tank for the past week (Back left) and when I do see him moving, he immediately goes back to that corner of the tank. I pulled him out of the tank and put him into another small tank overnight while I cleaned the tank and switched out about 40% of the water with new water about one week ago. I also replaced my broken filter with another one. The new filter is the same exact kind of filter I had the first time except my new one is for 30 gallon tanks while my last one was for 20 gallon tanks, I have a 20 gallon tank. He doesn't seem to be eating and he won't move from the corner. I think he may be dead but there is no bad smell at the moment and I know he moved yesterday. Is there any reason that he would stay in one corner of the tank and how can I tell if he is dead, basically, what can I do to get him to move if he is still alive.