The last lion is the radiata..its maroon and black, with two horizontal stripes on its caudal peduncle (the area right before the tail fin), it has pencil thin rays on its pec fins and no webbing. This fish gets about10-12" but grows very slowly. I have seen this fish have reds, maroons, blacks, greens....very beautiful, and the most expensive (about $60-90), also the least hardy of the lions-it does not tolerate poor water quality, and it is very particular in its feeding (it appears to like shrimp better than fish)-10 times more difficult in caring for than the volitans. You should be able to keep the lionfish together no problem, and they will actually help each other hunt for food. A herding behavior. Remember that lionfish are dawn/dusk hunters in the wild so there are not very active during the day, and on top of that very lethargic...so expect these fish to be more active when hungry, but hiding and "laying around" most of the time. It takes about 2-3weeks for the fish to adapt to a feeding day cycle, however none of my lions were ever shy about eating.
Feeding (short version): Right at first you should probably feed live foods...like ghost shrimp, guppies, mollies, rosy reds(minnows-do horrible in salt water), and goldfish (last resort). Once they are stable and happy (about 1 month), starve them for 4 or 5 days, then introduce small silversides (this is a marine fish which is sold as "silversides", it is packaged in 25, 50, or 100 packs, its frozen and full of nutrients). The key point here is that you have to link the dead non living food as a food source to the fish-since the lions are use to seeing moving wiggling food before they eat it. I wiggle the silverside in front of the lion and when he extends to eat it -let it go (obviously thaw them in warm water first).