I have the Avast ATO on a 65g w/sump, a Tunze nano ato on a 16g IM fw and 12g Mr. Aqua fw and the bigger Tunze version on a 75g fw tank. All versions have been up and running over 18 months, all tanks have snails in them, never had a problem with any of them. I will say both Tunze models do shut off after a minute to help avoid over fills in case of failure. I did look at the smart ATO, but at the time it was pretty new, plus the price point turned me off.