ATO for sumpless reef? Optical sensor vs Float

[mell0w]

I have a 55 gallon tank, it's not an AIO, I just run an HOB protein skimmer and some HOB media reactors. I've just been doing manual top offs daily (no lid) so it burns through like 1/2 gallon a day and it's sort of annoying to top off on my own.

I was considering an ATO to make life easier, and I was just about to checkout on an optical sensor one until I did a little research and people say that if you put it in your main display there's a chance a snail could crawl onto it and it would get stuck on and subsequently flood.

Is that true?

And if so, would I be better off going with a float valve ATO, even though those are prone to salt creep build up and could get stuck?

 

[Punchanello]

Most decent optical sensors have some safe logic in them. Mine will shut off and blink if if the refilling time is 1.5x greater than the average of its previous refill events. Both the sensor type and float valve have their advantages and disadvantages and can fail but the main thing is to ensure a failure is not catastrophic (like having a 50 litre ATO reservoir on a nano tank).