Just to chime in on this... I made one of these aero-cloners that I ended up giving to a friend of mine before I ever used it. He tried taking cuts a couple different times with a 24/7 pump and got stem rot. Then I believe he also tried using a timer and got the rot again, so he scrapped the aero-cloner and made a simple bubble cloner. He hasn't had a problem since. I made a smaller version for myself for about $20, and it was 15 minutes worth of work from start to finish to build..... It's the easiest way to root clones that I've ever tried, and I've literally tried everything. Change the water every two days and 7 days later you've got roots every time.