I should've added that they certainly aren't the cheapest heater you'll see. But I can't think of one piece of equipment with a greater ability to destroy a tank all by itself. Lights fail, pumps fail, things clog, etc, etc. But if a heater sticks in the on position and it's a one-heater setup, you're done. Nothing is a 100% sure thing. Nothing. If you need 200W, buy 2 100W Jagers.