I mount mine so the Pex connection is vertical, for something to get in it it would have to crawl out of the water, upside down across the holder, and down. I top off with lime; it will clog after having the ball valve off for a while that stops flow between the reservoir and float that a small blow frees. Fresh water will flow just like the one from the RO and i dont see a way without user error for it to fail; my ro float valve hasn't failed in over ten years. With electricity not only does the sensor side have to work, but the pump needs to start as well; it just doesn't pan out too well for long term reliability in my mind. Obviously a poorly thought out float valve could be just as problematic, but as part of a designed purely mechanical sump "kiss" is the best means IMO.
Back on topic that is a sexy looking ATO, if I had to look at something in a pico, that would be a lot sweeter!