My fiancee's clown loaches are swimming around on their side. Is this a normal behavior? Angelfish have been dying off mysteriously (3 of them, 2 of them were new so it could have been a bad batch.) Also, the clown loaches once went on their backs, and they do it in groups sometimes. Water params should be excellent, I change it 75% every 3-4 days, and it is a planted tank (no co2).