depends on how much heat light puts out. if house is constant like that in summer you should have no worries. just monitor temp and if it start swinging too much look into a chiller. There are actually some easy diy chillers out there you can put together for 50 bucks that work great on smaller tanks. Read the ratings on the heaters. If your close to the limit goto the next size up if it will fit. heater goes into the second chamber (opposite side of the protein skimmer if you got the hqi)