Ropefish are a very fascinating species. I had (past tense, old age) a fully mature 35 cm male. He was in a cichlid tank (Dempseys, Green Terrors, etc) and did not have any trouble. He would routinely bury himself into the gravel and just leave his head out, gaping like a moray! For the most part he ate small feeder goldfish, tubifex and sometimes freeze dried block. The rope was not really aggressive as such (except while feeding), but more territorial, of the whole tank :). It was very fascinating to watch and I HIGHLY recommend this species to anyone.
I've had a ropefish in a 450 liter cichlid tank for over 4 months. It's a very interesting addition to the tank, but until recently I was always worried about whether it was finding enough food. The cichlids devour any food I put in the tank within seconds, and by the time the ropefish picks up the scent the food is gone. I tried adding food after the ropefish emerged but the ropefish seems to hunt solely by sense of smell, which is no match for the speed of the cichlids. I found the solution in an empty Coke bottle. I placed a piece of frozen ground beefheart in the bottle and sank it to the bottom of the tank. None of the cichlids fit through the neck of the bottle, but the ropefish eventually finds his way in and gorges himself on the meat. This not only makes for a very happy ropefish, but is a lot of fun to watch - be sure to use a clear glass bottle.
I recently purchased 2 reedfish, a male and a female. I purchased the female a few days before the male. Neither would eat the small goldfish, zebra danios, small frogs plankton, flakes, pellets or frozen srimp I offered them. I could not find tubifex or bloodworms. I was distraught and thought that they would soon starve. In a last ditch effort I took earthworms and placed them in cold water to slow and purge them. I cut them into 3 cm pieces and now my reedfish are very well fed. So if you have picky ropes make sure the earthworms are clean and give them a shot. Another way I believe to tell the sexes apart are that the males seem to be a darker color than the females.
I have a Ropefish. I saw that many people said theirs tried to escape. Mine has never even attempted to escape. She lives in my 200 liter with my cichlids and never chases them. I found that they like to have dark spaces to hide in...not plants, but rocks. If enough space is provided for them to hide in they won't try to escape.
I've had two ropefish that were my 2 year old sons "Caterpillars". The first one was attacked by my Oscar while I was cleaning the tank. I jostled his lair and he came out and our oscar attacked him, causing internal bleeding. My son was constantly searching for his "caterplillar" and opening the cabinets to look up underneath the tank to see him in his rock so I had to purchase another one. This one did fine as well for about 2 weeks and one day we walked into the house after having been out for the day and the rest of his 20 cm were hanging out of our Oscars mouth, he had eaten him head first. Luckily our son didn't see that. We had him in the 380 liter tank, so I don't think the size of their habitat was an issue. They are wonderful fish, very personable and enjoyable to watch. I fed them prepared fozen foods, bloodworms, etc, and live fish as well. They are very hardy, I just recommend being very wary of whom their tankmates are. We're planning on setting up another tank of less aggressive mates and getting another one.
I've found a very clever way of keeping calabaricus in communal tanks without heavy planting or large rocks. Purchase a length of flexible ribbed tubing at a hardware shop, about 3-4 cm in diameter, and place it under the sand substrate with just the ends showing at the surface. Mine are quite happy in them and I don't have to switch off the lights too early, which means I get to enjoy the other creatures later in the evening. Mine don't seem to be shy, I see them all day long now for a few minutes here and there.