I have 4 GBR's in a 29 gallon that is heavily planted. I just put them in the tank last week. They're really small and according to the folks at the LFS, they're the smallest that they've ever gotten before.
I think the group is 3 females and a male. When I got them, their colors were a bit washed out and it was tough to tell what sex they were. I'll take how they ended up...hopefully there wont be any territory disputes.
Anyhow, I came home from work today and the male was attempting to chase glass shrimp away from what they were eating - a bunch of small white eggs! The GBR's are only about an inch long and already spawned, but I have about 8 (no idea how many) glass shrimp in the tank and they made a quick snack of the eggs. The male GBR was trying to chase them away, but they're full grown and at least half again as long as he is.
I hope this wont happen in the future once the GBR's grow.
Looking forward to seeing more from this group!