Take down a tank? Are they 300g+?
Is it a reef set-up with heaters, chillers, and halides?!?
Try taking down a fridge, space heater, de-humidifer or something that actually draw some real power..
My family members accused my fish tanks of being the source of our 'outrageous' electricity bill last winter.. It wen't above $300.. they all SWORE it was 'the large multiple fish tanks in the garage'..
Gee, winter passes and with all of those 'large multiple fish tanks in the garage', the Bill went back down to $100.. just like before I had the tanks plugged in. Space Heaters in the Winter was the culprit!!