Originally Posted by gilbert
As far as lionfish specifically go, that is pretty much correct. Lionfish don't really have the teeth/mouth to eat coral. They will however eat other fish that are small enough to be palatible.
Other aggressives, like some
species of triggers and puffers, might nip coral to grind their teeth on. Also triggers are known to pick up smaller coral frags, and use them sort of as a toy, dragging it around the tank.
Generally you don't see aggressive reefs for a few reasons. This will get a bit ranty... The obvious one is that most clean up crews will be eaten. It's been so ingrained in every aquarists mind that CUC are absolutely necessary, when in actuality that couldn't be further from the truth. Proper feeding habits, stocking levels, filtration/etc, will prevent the need for a CUC. Secondly, is bioload. Most aggressive fish put a sizable bioload on the tank. Generally speaking, most people who kept FOWLR's tend to just put up with poorer water conditions (not actually poor, just nitrates levels that would unacceptable in a reef tank). To stock a reef tank with the typical amount of fish a FOWLR has, you'll need massive filtration, and a stringent water change table. Third, cost. Most aggressive fish are aggressive, because they are large fish, and need an accompanying large aquarium. Large FOWLR tanks and medium reef tanks are typically negligible in costs. Large reefs, are obviously a pretty penny to run. Finally, and this is perhaps IMO the biggest hurtle, experimentation. People tend to unwilling, rightfully or wrongfully so, to risk mixing questionable fish in with their corals. It will take a bit learning to decide if that Clown trigger is safe will just SPS, or what happens if I mix in a large brain coral? Since every fish is different, there is only one way to find out.
I hope I didn't long too run and elude to an attempt to suggest against the idea of an aggressive. Quite the opposite.