Most books and literature recommend a heater running about 78 degrees F. I've run many aquariums with no heater but room temp being kept at 68-70 degrees. My tanks had zebras in them an they did fine. Most heatere have a manual adjust with degree markings.

i would love to do some reading about fish, but obviously i am not a good reader, that's why i came here.:P
i'm wondering where i can get a cheap and good heater because someday i will put some other tropical fish in my tank. The zebras there look rather lonely.