Hi Dru,
Yes, they will add more heat since they uses more wattage, but the pendants do a great job of keeping the heat above the tank and off the water's surface. They hang up higher so you don't have to worry about direct heat transfer, owing to the glass shield and vent slits in the painted housing.
One or two IceCap 120mm fans blowing across the surface will easily keep the aquarium chiller-free, with very low wattage use. You'll want to put those fans on a timer to turn them on for the exact amount of hours needed, and no longer. Otherwise the tank may run too
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