What I would do is see about getting one of these Kill-A-Watt meters, and then testing every piece of equipment on the aquarium:
http://the-gadgeteer.com/review/kill..._usage_monitor
Once you have that info, you'll have a better idea if your bill is wrong.
I'm not sure where you can pick up one of these Kill-A-Watt meters. I did a search at canadiantire.ca and came up empty. Maybe Home Depot or Rona, or Home Hardware type places.
Or you can check out ebay, about $20 for one that way:
http://search.ebay.ca/search/search....att&category0=