These are not in an aquarium, they are wild in the Philippines. I've seen a lot of lionfish, but they looked different. Very long fins and jet black instead of the more common red or brown. They were medium-sized as far as lionfish go - not a dwarf species and probably not juveniles, but much smaller than some of the huge P. volitans I've seen. You can't really tell from the photo, but they are much darker in coloration overall than most lionfish - both the darker black, and less light area. I've posted on other forums and not had any luck getting an ID, so I thought I'd try here.