pretty much loners, i have one in my 75g with africans. they really like hide, you may only see it once a month if that. but there pretty cool do a good job cleaning and i happened to see some full growns ones at Aquarium Oddballs in Tulsa and they kinda just lay around. But one i fine
I have two of these guys in my 50G community tank. Simply amazing fish - mainly because they never bother anybody else - except that they probably dont seem to enjoy the sight of their own kind. I guess these fish max out at about 4 - 5"
I've seen pictures of river ones that were pushing RTC size (about 3'.) I have a spotted one and he hasn't grown a whole lot since I got him. He's only about 3" and I've had him for more than a year.
The big ones you saw were probably megaladoras species. The common raphaels are very small, and never get very big at all. Megaladoras are often refered to as giant raphaels.
I have one Raph in my cic tank, he only comes out at lights off time, but is quite happy to jig about with everyone else and he's quite a nice looking fish.