You can breed them in 10 gallons, but in my experience the bigger the tank, the mor eprolific the pair. I have 2 pairs of azureus. One pair is in a 40 gallon tank and one is in a 10 gallon. The pair in the 40 lay once a week and lay clutches of 5-6 eggs with usually only one egg per a clutch going bad. The pair in the 10 gallon lay every 2-3 weeks, and only lay 2-3 eggs, often only one egg will hatch. Both pairs are the same age and I raised them from froglets. I think a 20 high would be a good compromise. especially if you have the room.