Tank Heaters - question

[mike31154]

I use two 150 watt heaters in my sumpless 77. Need to tweak them up during the cold season since I allow the room temp to drop to 16 C overnight. When I set up the tank I was using a single 300 or 350 watter. Changed to two for the reasons Myka mentioned, if one fails in the ON position, I should notice something's up before my critters get roasted.