My breeding tank is 2.2 US Gallons. 12" * 8" * 8" and i used to breed guppies and put them in there. They loved it!. I put a tiny filter and heater in the tank. I also used a rena 100 with a singly air stone close to the heater. I also decorated the tank with a few fake plants and rocks. I used to have about 300 fry in there once and then i fed my fish some contaminated frozen food before i went on a day trip out. Got back and 80% dead. But nevertheless, the fish loved it. I also had a car light bulb as a battery, but i wouldnt recomend that. Just buy a 12" sun glo flourescent tube.
I got a pic of that tank on my profile. Its a different layout now and i ditched the air stove and replaced it with loads of plants and CO2 on tap, this is probs a nicer environment for your fish too.