I currently have an aquarium with a Tiger Oscar that is about 2 inches long, various other smaller fish, and a blue crayfish that is 2.5 inches long. I am planning to build a Plexiglas box that is submerged with a structure allowing the crab to crawl into the air bubble easily. It is fed air by an air pump that constantly feeds air into the bubble box. It is a 55 gallon tank. My question is will a crayfish and a crab be able to live in peace in the same aquarium? any suggestions?