Hi, I've been kicking around the idea of building my own ATO. I know that this is easily doable with a modern controller & a couple of float valves but I want to take things a step further, I want to put together a stand alone ATO that does not rely solely on float valves but I want to incorporate optical sensors (sort of like Tunze Osmolator). My current concept incorporates the following... Either one float switch & one backup optical sensor on the sump DC powered everything or DC sensors triggering an AC relay that fires an AC pump I would love to do an all DC system with 2 optical sensors one in the sump & one in the DT the sump sensor will trigger a 12v automotive relay powering a brushless pump when water level drops, the DT sensor would be an absolute in case of emergency type thing where it would shut the entire system down (except powerheads) if water level rose above the sensor. I like the idea of doing everything DC that way i can DIY my own power back-up & run everything off a car battery in case of power outage... Nevertheless I want to hear about your designs whether it's like this or totally different, just for the drawing board. Thanks.