Depends on the type of polyps. Some won't really need to be fed. If they extend "feeder tentacles" then you can try to place some chopped food (like the frozen fish food, chopped up so that the bits are smaller) onto the tentacles.
For mushrooms and zoanthids, you don't really need to feed those. Button polyps you could maybe feed, but I don't know if they really need to be fed.
As for clownfish, they go through an interesting cycle. They start off in life as males. But basically undeveloped males. In a pair, or a small group, one will basically be the most dominant, and that one becomes a female. Once female, they can get larger. Depends on the species how much larger. For example, maroon clowns, the female is like 3" - 4" the male only about 1" - 1.5". In percula clownfish or ocellaris clownfish (they're nearly identical species) the female only gets slightly larger. If there are two fish, then the other fish will be the male. He will stay smaller. If there are more than two, then the "second in command" will become the mating male, and the others will be undeveloped males (i.e., they can't sneak off with the female and do the wild thing behind the #1 male's back.
). If something happens to the female, the male will become the female, and the next in line male becomes the mated male. And so on. If something happens to the #1 male then the next in line (the #2 male) becomes the #1 male. This group of fish is sometimes called a "sharem" (opposite of "harem" -- one female who rules the roost, and a bunch of males).
Anyways the short answer to your question then, is, the female is larger, and the male is smaller. But if the fish are young (i.e., under a year or so), then the roles may not be clearly defined. And they may have the occasional skirmish to see who's the "toughest" and thus steps up to become the female.
Some species of clownfish (maroons in particular), it is dangerous to have two undeveloped fish the same size, because they may kill each other in the ensuing fights to establish dominance. Luckily, ocellaris clowns tend to get along with each other a little better than that.
