I looked into my tank yesterday and one of my tiger barbs was having trouble staying down. He kept floating to the top of the tank, he wasnt dieing or anything, he was trying his hardest just to keep swimming down, but eventually he just got to tired from the constant swimming down and gave up, so he ended up just floating at the top, but still breathing normally, and he even ate some flake food that i gave him. However this morning he was completely fine swimming around as usual. Does anyone know what would've coursed it to loose its ability to swim properly for that short period of time?