This looks like a good system. The only thing I would do differently is wire a new receptacle in the pantry using the existing wiring behind the light fixture. Those adapters are typically rated for only 660 watts. Any more than that and there is a fire hazard. But if the heater, one pump, and the light bulb add up to less wattage then its ok.
Plumbing the tank drains directly to the house sewer line makes a big difference. Before I did that my wife was getting tired of seeing fish tank crud in the bathtub.