If you have one or more tanks in the room that need more heat than your room heater can provide, you can always put individual heaters in those few tanks.
That's a very good point. I don't think I'd get rid of my heater collection if I moved to a central heater just for that reason.
My fish room is only 10x12 and this doesn't deal with humidity. I had to open windows in January because humidity was cresting 60%. not looking to rot my house from the inside out....
Whiteram gave me advice about using a dehumidifier to heat the room while remove the moisture, 2 birds, but not efficient. All in all operating cost would be a wash.
I have been running a dehumidifier as well, which helps add some heat to the room. I also have my wood furnace in the room immediately outside the fishroom, which is the worse insulated wall simply due to the door, so in the winter it helps to buffer the ambient temperature when entering/exiting.
I've spent a lot of time thinking about this topic over the years and I don't think it's possible to save operating costs if the choice is between electric heaters in the tanks and an electric-powered heater for the room. The gas heater like jamarini mentioned would help save cost since it's often more efficient to heat with gas than electricity.
The big advantage I see is to save costs on buying/replacing heaters on a tank by tank basis. Liberating myself from another $20 heater per tank makes setting up extra tanks just that much easier.
Variable wattage oil filled electric space heater works great, i run a 15yo version of this link: http://www.lowes.com/pd_167509-47166-73368_0__?productId=3468001&Ntt=oil+filled+space+heater&pl=1¤tURL=%3FNtt%3Doil%2Bfilled%2Bspace%2Bheater&facetInfo=
I'll have to go take a look at that. From what I've researched so far it seems that many oscillating-style ones are bad news over time because the cord weakens due to continuous movement within the heater, leading to a greater chance of fire. For a smaller, well insulated room a stationary one should work out fine.
