I have a Tunze nano auto top off with a float switch. I was lucky enough to be around when a stomatella snail decided to crawl up and block off the float. I am usually unable to see my fish tank for two days on the weekends and I am concerned about my main pump burning up when the ATO shuts off for safety and the water level gets to low. If anyone knows a better solution I am all ears I am tempted to purchase a different ATO system with multiple sensors or maybe fabricating a screen net around my single sensor?