they are harmless pods, tiny in size, and your clownfish eating them.....that's perfectly normal. the ones with really long antennas and look like a miniature version of a roach is an amphipod, again...harmless. Just showing you signs of a healthy tank there, congrats! :lol:
also if you still worried about them, I guess you need not to worry much as the clown will eat up all the ones on the glass...the rest will end up in rocks and stuff where you wont see them as much.