I don't think there's a wrong answer. I doubt the ghost will interreact with the cats. As long as each gets enough to eat they should be ok. Are you sure they don't come out after dark?

Hi James - I guess I'm just concerned about each, the BG & Felix the cat's "territory" and how they will react if I switch tanks on them. Do you think the other two will be O.K. with the BG? I don't understand your question about the dark. They all are active and come out during the day or anytime they see me and know food is on the way. I don't keep their lights on because there's enough natural light in the room the tanks are in (my office). Let me know if you have any other ideas. Thanks

I agree with James. Fish are like people in that if you break the "pecking order" and start them in new (to them)environs, they will establis or re-establish a pecking order.

Also, what would be really helpful with shy and/or territorial fish is to prvide lots of hiding places, whether it be plants, shale, driftwood, PVC,...

When your said your cats stayed in one part of the tank I assumed they might be nocturnal. Many fish are not territorial especially with other species. If this is the case even if you left all 3 in the 55 they should be ok. I recently bought a thermometer knife fish [@ 8" long, white with brown bands] and have only spotted him a few times in my 150gal.