I had a single lyretail at one time, a male version with the red skin and long spine, really fun fish to look at. I would feed daily, and he seemed to do fine for a few years, however I did (do) have a small fish population (5 fish in 180gallons) so it is conceivable that there was enough "food" in the tank for him to sustain himself. I've always wanted to go with a harem (orange females) because those are the shots of tropical reefs that always impressed me the most 100s of orange buggers swimming around a rock wall or something. He did die of unknown causes, it could have been negligence it may not have been negligence I really don't know. If I were to go again I would definitely go with autofeeders and multiple times per day (I do that now actually), still would have a similar fish/gallon ratio though perhaps run a large refugium in the hopes that "food" does make its way to the tank (although I'm not quite certain you can do that on a large enough scale... although the low fish count certainly helps).
Can't say if he was aggressive towards the smaller fish because the only smaller fish were a couple of Talbot damselfish, which I've heard are a bit more of a mellow fish but they're still damsels
