I came home from work today and seems like my young gar(7") is having a hard time staying upright. It is trying to swim but keeps barrel rolling. Does not seem to have any problem using it's fins as I can see it's trying to counter act whatever is causing it to flip over. No signs of bloat or injury. The gar was perfectly normal yesterday. None of the other inhabitants of the tank are having any issues. The tank is a 120g 2x2x4' pH 7.8 ammonia 0 nitrite 0 nitrates 40ppm 80°f , any thoughts or suggestions are appreciated.