I have 2 rope fish in my 100 gal. tank, but had 3 in my old 75 gal. tank. I would say 55 is fine for 2 of them. Rope fish are very unique fish. They are almost blind, they find their food by smell more than sight. They are very passive fish, and will run from a guppy, lol. I started out feeding them ghost shrimp, and frozen bloodworms. Now they will eat shrimp pellets, and even fishfood that drifted down from the top, as well as bloodworms. They are mostly nocturnal, I sometimes only see them on cleaning day. I love mine, but I wish they were more visable. They hide for days at a time. They will eat a fish they can catch at night sleeping, but I have guppys for them, and my guppys are breeding faster than they are eaten. They definately are snake-like. My mom hates them because they look so much like a snake, esp. when they come to the surface to get a breath of air. Some say they are escape artists, but mine seem perfectly happy to stay where they are.