I recently bought two clownfish which have adapted to my tank very well...at least I thought. They are both eating and interacting wonderfully, one just is acting strange. He swims, extremely fast, back and forth across the top of the aquarium. The other fish act normal and don't seem to mind, he doesn't act sick. He just has decided over the last day to do laps. Is there any reason for this...or just a weird personality?