You have a pretty deep freeze line up there from what I found on the net. 24 to 30"
If the tank were below this line, then heating wouldn't be so bad. In fact it would help keep the heat down in the summer.
You would be looking at commercial grade heaters for a tank that size regardless. It would cost you probably 50 to 100 a month just for the power to the heaters!
This is one of the things that a lot of folks don't take into account when building really big tanks; the ongoing cost of power.
I helped (in1992) build a 3200 gallon shark tank in a garage with the glass into the living area of a home in Alabama. The tank was concrete, rebar and chicken wire then coated with water tank paint. The glass was laminated 2" thick. The tank and filter system only cost around $10000. The problem was, even with the very low lighting, the electricity was over $200 a month on a seperate meter.
This is the only thing that has kept me from doing it myself.
When I do an addition in the next few years, I am planning a room that will have it's own a/c unit and have the ability to vent humidity to the outside. This room will house the tank (12 x 6 x 5) the 1000 gallon+ filter system and related.
Just the room will cost in excess of $5000 to build over the rest of the addition, and that is not counting the $10000+ to build the tank and stock it.
I don't mean to discourage you. Quite the opposite, I want to see folks really do this well and be able to keep it instead of tearing it out in a year when they realize the maintenance and ongoing costs are astronomical.
speakeraddict