The divider idea would be ideal, less stress on the fish and you wouldn't have to worry about cycling a new tank. I would use the 10 as a grow out for the fry once they are free swimming because they might fit through the holes in the divider at that stage. You should be quite proud of yourself, lots of people keep fish but it doesn't mean that they have their fish happy enough to breed. Now why are you worried about the bichir? he shouldn't be a threat to the rams at his current size and not for a while at least.