Levi has recently starting resting a lot more than he used to. He looks fine, is eating fine, swims up most times when I look in the tank and always comes up to be fed. No laboured breathing or anything to be concerned about really, except the fact he's almost always on the floor! It's the change in bahaviour that's bothered me, he always used to be midswim when I approached before. Is there likely to be anything wrong?