I have a gallon and the other one is swiming in a bucket with 1.5 gallons and I never really had any heating issues with the gallon. I got a Marina heater from petsmart. Someone is letting me borrow their other more expensive heater for the other one and it's not really working to well. But thinking about it now I would have to agree with the smaller tanks are harder to heat. Especially the gallon because I have to adjust the lid to control the tempiture. The colder the outside air the more the tank needs to be covered. The warmer the outside air the less covered the tank needs to be (or it'll over heat). I'm excited to get my 5 gal going so hopefully I don't have to play games with the heat anymore... And all the water changes. My ten gallon is a lot easier to take care of then both my smaller tanks.