I'm sorry but my ropefish is the farthest thing from predatory! I've tried feeding it live food and its absolutely terrified of it. I also agree that it doesn't need a huge tank. Their bodies are actually pretty small and its not like they array some huge bulbous Oscar.
I haven't heard anyone with a elephant nose in a community tank that hasn't ended poorly.
Back to the elephant nose idea I do t see anything wrong with it as long as you are ready to feed frozen foods each day. To help getting him to eat befin feeding him some live black worms mixed with frozen blood worms. thats what i did. Just make sure when picking one out it is nice and healthy and ask about his history at the store. I've had mine for over a year now with rainbows a red tail shark. Some peacock gobies. Glass cats and even Cory's. mine is such a pig at feeding time I sometimes feed every other day because he gets so insanely fat.