I have two little clown loaches that seem to swim odd. All other loaches I've seen swim pretty fast and have no problem moving around to get to the top of the tank for food. This is not the case with mine, it seems like they have a hard time swimming to the surface for food. I'm not concerned about them not getting food for the pellets they are fed sink but I'm worried somthing might be wrong with them. Is this a needless worry or could somthing be wrong?