This morning i noticed my guppy is swimming on his side and i can't figure out why he is doing this. There are no other fish in the tank with him so I know that no one is stressing him. I nitrates, nitrites, ammonia and pH fine. I did a pwc yesterday, and I think I am going to another one today and tomorrow. I do seem to notice him going up to the surface only during the night and staying there, I thought he was gasping for air so i but a bubble thing there, so I don't think he is oxygen deprived. The only thing that I was suspecting was that maybe it could have been the temperature yesterday since it was a bit on the cool/ cold side but it didn't affect my betta at all, so I don't think it was that either, plus since this morning it definetly heated up a lot. Please help me. Thank you very much for your help.