I have a leopard ctenopoma. Most people tell you that it takes years for them to get to 6 inches, but my experience is different. I bought my leopard ctenopoma a year ago at about 1 inch. Currently, it is over six inches and still growing. I fed it three times a day when it was small and feed it twice a day now. In terms of feeding, when I first got itm I put it on hikari carnivore pellets by splitting the pellet in fourths to make sure it was small enough for the ctenopoma to eat. After getting it to eat that, I added krill and chopped up red wriggler worms to its diet (I now use cut up small earthworms which are thicker than red wrigglers). I made sure it ate pellets everyday and alternated between krill and worms every other day. I paid about $11 for my baby ctenopoma a year ago.
I would advise that you get a ctenopoma while it is small and avoid buying ones that are already large. If you buy one large from your pet store, the fish tends to want to eat feeders only and are very difficult to get off of feeders. My first ctenopoma was like this, so I got rid of it. Also, it was very aggressive as it fought constantly with other fish in my tank. I think this may have been because it had been fed feeders for so long. I never put feeder fish in my tanks. The internet tells you that they grow up to 6 inches, but 8 inches is more like it.
My leopard ctenopoma is usually mellow, but it will occassionally take a snap at one of the silver dollars or chase the slightly smaller thinbar dat every now and then. It likes to chill out with my small clown knife in its cave. You could probably mix the ctenopoma with some gouramis if you get them small and similar-sized. Depending on your tank size, you may want to throw an angelfish in there as well. Just make sure that the fish grow up together.