I've had 2 ropefish for 4 years, they've never eaten a tank mate, not even fry. Once mine got comfortable they started comming out in the day a lot. As for food, I feed mine beef heart (which they never turn down), crickets, worms, and sometimes they'll go for shrimp pellets. I'd say get one, especially if you're a beginner since they can tolerate a wide variety of water conditions and aren't prone to disease. Be sure there are no ways to escape because they will get out.
i have had my ropefish eat my young swordtails and minnows. i throw in earthworms and they get them in seconds...just make sure the lights are off if you have larger predatory fish, so the ropefish has a chance to catch the food.