I had a Prism ato that stopped working recently, so I sent an email to reefbreeders and they got back to me the next day and asked me to do a little troubleshooting with a multimeter. Which I did and was getting power from the power supply but nothing from the sensor. So I emailed them back and they said yup looks like the sensor is bad we've shipped you a replacement unit. I got a shipment confirmation right away and the replacement showed up a few days later. It was so nice to deal with a company that is responsive and stands behind their products. I was a little worried because I'm getting ready to go out of town but they got me all fixed up strait away. I already bought another prism for my wife's biocube and would not hesitate to use their products going forward. I cannot speak highly enough of reefbreeders.