A pair would be fine if its a 24+ gallon, anything smaller you could go with dwarfs. I think you will have temp problems without a chiller especially this summer time unless your house stays cool. Luckily I keep my tank next to a window unit and I actually keep it steady at 72 degrees all day long with no chiller. If the tank is already setup try and observe your temp readings everyday and night to see how bad your swings are and that will tell you if you are going to need a chiller or not. Good luck!!!
