i paid 40 but mine is over 2 feet. It would have to be a huge Cichlid because when my guy eats 4" large goldfish he bends them in half long ways, before he swallows them whole! He eats them from the side. Not once head or tail first. This is an awesome example of strength. So look for something atleast 6". If he cant eat it he wont bother it. He is not aggressive at all.
I have an 120gal with a bunch of random fish: Large Gouramis(Gold, Opaline, Blue), Plecos, Electric Blue, Red Peacock Cichlid, Zigzag eel, Large Golden Algae Eater, Probably the largest white female molly ever, Leporinus Faciatous, 1' clown knife, 1' Black Ghost Knife, 1' Brown Knife. Some less aggressive fish but doing great in the tank are some emerald cory catfish, barbs and rainbowfish. But I always keep a large school of rosies minnows in the tank as a constant food. This helps to keep the predation way down.
I also do this with the eel tank and my brackish tank.
A 80 gal Brackish 4 archers, 1 snowflake eel, 1 sand/marble goby, freshwater lionfish, school of monos (5).
And a 12 gallon Saltwater Nano-Cube!