I understand you'll be getting a much larger tank when you move, earlier you mentioned the possibility of using a 75g temporarily. Do you have the 75 now? Is it occupied?
Just wondering if you could split the group or move things around. I imagine how cramped that 55 is looking for you... I have a 135g and I'd love to add more bleeding hearts. But then I think "when these guys get some size, if I do get a harem, will the tank feel too full with 4 or 5 GT's AND a bunch of bleeding hearts?"
Decisions, decisions...

As far as your tank goes, how large do bleeding hearts get? I'm not too familiar with them. If the 135 is rather deep and not so tall, I could see it working... but if it's a standard 6 footer and is only 18" deep it may be an issue when the Rivs reach full size
Decisions is right! lol