If your angels are still small, they won't breed because they aren't sexual mature yet. I think my angel is old enough, but he's almost 5" from nose to tail. The best bet if you want them to breed in an isolated environment would be to get a MINIMUM 20gH tank and use that. Once they lay the eggs, remove the parents back to your big tank. Anything less than a 20gH will be a waste of your time and money if it's for the sole purpose of breeding your angels.
Random announcement...I was bad yesterday. I went to Petco in a different city (was taking some friends to the Amtrak station 2 hours away) and walked out with a GORGEOUS dark blue mustard gas male halfmoon doubletail plakat betta and a matched pair (m/f) of neon swords. Now I have to juggle more tanks to fit Emmett (the new boy) in. Aidan is going in the 6gal FBH and Loki is going in the 5gal bowfront, so Emmett can have the 10gal all to himself.