I actually just got an Aqueon 100 for my 29 gal. I wanted to switch some fish into it, but got frustrated when it appeared my little sticky thermometer kept showing the temp as being lower than I needed. I scoured the house and found a digital thermometer. Much like something that would be used in scientific experiments (mother is a science teacher). The temp was exactly where I wanted it. Point being, if you think you are having trouble, double check your temperature.