okay i just quickly skimmed through this thread so i apologize if this has already been mentioned.
cmopatability: this is a very peaceful fish. the only reason we can classify it as "aggressive" is the venom. size has already been mentioned. I would be most worried about mean fish and fin nippers like triggers or puffers (although some cases have worked fine).
venom: the venom is not fatal unless you have a reaction. best thing to do is call 911 immediately and let them know what happened. it is protein based so run the stung part under water that is as hot as you can stand without scalding yourself. Application of corticoid creams help to ease the pain.
Volitan lions can get up to 18inches and need at the very least 100 gal. I would give it more. If you want a lion whose minimum is 75gal becasue it stays smaller, then pterois russelli is a great choice. russelli lions are easy to distinguish from true volitans if you know what to look for, but are often mistaken as volitans.
the easiest difference is the banding patterns on the body. volitans have a denser pattern of thin stripes. russelli have bandings of mostly broad stripes (with significantly less thin stripes than volitan).
for example...
ram 74: your lion is a shining example of a beautiful lion. note that the banding is dense with thin stripes.
dr BDC: your pic is that of a clearly stunning russelli lion. note the broad patterning (relative to volitan) on the tail in that pic.
drBDC, I don't mean to put your lion down. I actually generally prefer russelli over volitan because they're pretty much the same but smaller versions of their cousins. gorgeous specimen.
for more info on different species of lion and good pics to compare them...
http://www.reefkeeping.com/issues/20...ture/index.php
i think this was referred to but wasn't linked.