Undersizing a heater in a midsize sumped setup?

[Blorton]

Getting ready to fill up the 75 this weekend and wanted to bounce this off the collective:

This tank will be in the insulated basement with ambient temps no lower than 65-70f year-round. The tank will have a total water column of perhaps 100g, 150g tops if I nut up and run one of those horse troughs for a sump.

To start with, I'll be running a submerged pair of mag5's (skimmer + return) along with several powerheads in the tank for water movement. With all that radiated heat in the water, wouldn't it be safe to say that something like a 200w heater in the sump would be a gracious plenty? I know during the day that lighting will keep things warm enough.

Thanks!
Dan

[tims]

in therory yes that woudl be fine, but i rather have one or two heaters that would do the tank if it was not in that area.
you can always dial down a heater.