Ecomical space heating

If you have access to natural gas or propane, you might want to look at ventless gas heaters. Units with thermostatic controls start at about $125 US and can be found in home depot.

Good Luck,

Chris

radinent heat sorry don't know how to spell it

If you have to use electricity you can make a window heat pump out of a window air conditioner but it required some modification.

Otherwise, why not just put heaters in the tank?

This is a bit late.

But my guess it that there is enough sun all year to set up a solar heating system. It can be as simple as a few meters of black hose lying in the sun, circulating to a similar setup inside.

Do a search for DIY solar, and you might get some ideas.

If the temperature drops a few degrees during nighttime, that will probarbly be fine with most fishes, not to mention that water works great as a heatsink.

A late advice too but from experience.

A dehumidifier is a must in a small room full of aquariums. Besides taking care of the humidity it also heats up the room at least 15 degrees F.

But I don't know if it uses tons of electricity. It's basically an window A/C unit working in a little different way.

--Nikolay