Thanks for the input guys!

Tom, you mention that you use two of them on your smaller tanks. Are these not as efficient as in-tank heaters? I run my 26 gal with an in-tank heater and keep the temp around 77. I have two toddlers, so I do not let the house temp drop below 69-70 in the winter. Do you think I can keep my 75 gallon stable with a 300w on each cannister?