Being an ambush predator, I believe they are most comfortable in a tank with tall driftwood, soft water, and surface cover. My tank has a number of large Val's that grow to the surface and trail over about 1/3 the surface area. There are a number of small water lettuce cover approx. 1/3 the surface as well, with lots of crypts on the bottom. I'll be adding some driftwood and more plants from my main tank this weekend.
Not particularly picky and certainly not shy. None of them hide and as a group they are found, and eat, in all parts of the water column. All will spend at least part of their day hovering over the crypts looking for missed food in their classic curl tail posture. They approach the tank looking for food as soon as I come near (they are absolute gluttons) so I need to cautiously approach to see their normal behaviour.
Please bear in mind that this is my first experience with Ctenopoma, I don't claim any expertise.
O