Worked great for about 6 days. Today it emptied my reservoir into my tank. There was no power loss or anything that could have made it freak out. Thank goodness I leave my water 4 inches under the top edge as it can not fill to the point of trashing my house. The QST or whatever it is called must be made up because I didn't get any sort of alarm or cutoff and to empty my reservoir would have taken quite a while. Like at least 200-300 times longer than how long it takes for one fill. Fish are dead but no high dollar fish in there, its the coral loss that could cost 5 digits. Ultra low nutrient tank and the sensor is still shiny clean. If I manage to save the coral and it doesn't do it again ill update the review for another star but at this time I don't believe the safety features are real and will have to implement my own secondary failsafe to cut power if it goes over the sensor. This was supposed to make the tank easier, not take even more time than adding water myself.Update: Most coral survived but it tried to do it again 4 days later. Again no condition to set off something weird. I installed a large float valve on the outlet. Walked into my office with the pump trying to overpower the closed valve. I have no idea how long it ran but it could have been trying to overfill for hours. This time I was ready and saltyness stayed tolerable. I'm just going to cut out the controller and use an arduino..This ATO works great only draw back is the safety valve that causes water to leak where tubes join. I just keep that section over the tank so I don’t cause leaks onto the floor. Other than that satisfying results.Functions well, but only lasted one year.Used for 10 days and unit failed. Sensor was filled with water. Called support and sent replacement immediately.Will give it a try one more time given maybe I got a defective unit. Will update review.Can’t recommend this unit at this time. One thing that I would recommend in the next version would be a way to replace the sensor.Bought this to go with the innovative marine 5gal reservoir. Looks really nice, super easy set up. It is very quietReplaced the “other” brand version of this. The old one lasted 12+ months before the sensor died so I’m not complaining. They seem to work the same. I was able to use the auxiliary pump module with this (so I could use my own ATO pump). For those who may want to know: I have extended the pump power cord 60+ feet to my water mixing station and it works great.