Rummynosed tetras, Black neon tetras, and Cardinal tetras are classic fish to go with GBRs because they all enjoy the same warm temps.
Keep in mind you'll want to keep this tank in the low 80s F if you want to keep the rams spawning and in the best of health.
I'd start off with a half dozen rams and let them pair off on their own. You may be able to keep 2 pairs in a 55gal if you use plenty of hardscape to help block off territories and aquascape so that the lines of sight are broken frequently (rams wont chase other fish once they swim out of sight).
If you really want to raise fry you'll need to set up a separate spawning tank, though- you won't get many fry that survive any community tank setting.
Keep in mind you'll want to keep this tank in the low 80s F if you want to keep the rams spawning and in the best of health.
I'd start off with a half dozen rams and let them pair off on their own. You may be able to keep 2 pairs in a 55gal if you use plenty of hardscape to help block off territories and aquascape so that the lines of sight are broken frequently (rams wont chase other fish once they swim out of sight).
If you really want to raise fry you'll need to set up a separate spawning tank, though- you won't get many fry that survive any community tank setting.
