Hi , just trying to buy an auto top off , but confronted with some problem about one. I've tryed the one with optic sensor and it didn't work. Suppose to be the best , better than floaters, what do you think. Floaters or optic sensors for you. For your info, optic sensor don't work near other pumps and magnet of anykind. Thats the one i tried and it was overflowing; the pump magneting field apparently was disturbing the sensor. at the store it worked fine and in my biocube , forget it. But the question stands wich is really the best or necessary, by which i mean reliable for the price.