in captivity it is not unreasonable for them to grow about a foot long...with the space they need anyways...
feeding habits...well, if you really want to see something cool, you should give them their own tank which should be long and shallow, will plants like jungle val, and some reed type plant, like even bamboo or fake/dead bamboo reeds...they will hide in the reeds and act like a plant since they are so laterally compressed...hence compressiceps...and you could feed them live and its a joy to watch them stalk and strike.
but you can feed them just about anything else, even veggie pellets, i feed mine hikari cichlid staple, gold, and frozed brine shrimp and blood worms...and every now and then they get a live treat from my disease free!!! feeders.
they are one of the only fish who will eat live food tail first, which is cool to see!
i have a pair and they have been one of the most gorgeous and fun fish to have, you will grow fond of it soon.
hope that helps