Well you say you did the obvious of setting the heater at its lowest setting...
I have never had an aquapod but I read about it here:
Aquapod | Current What's Next
Looks like a pretty sweet setup. Is your thermometer on the opposite end of the tank as the heater? I'm also curious as to how the flow is in the tank, if its turbulent or not.
Some things to consider, at least.
Alternatively, try and consider taking the next step and investing in a controller such as the ReefKeeper II, AquaController JR, or something similar. They are entry level controllers but pack some cool features. It'll kick your heater off much quicker than it's built in rheostat. The controller's hysteresis is adjustable to even a tenth of a degree, so you can keep the temp extremely stable.
ReefKeeper II and ReefKeeper Elite -
Digital Aquatics 2008 - Systems
Also consider the less expensive AquaController JR -
Neptune Systems - AquaControllers - AquaController Jr
The smaller the tank, the harder it is to keep stable. A controller should solve the problem for you and also give you insight into other things that are going on in the tank. Wish you the best, hope you get it sorted.

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