Mine has been running 24 since this post and I love how quite it is. I am not sure if GH pump is the same as the one I had was (you can see it in the pictures on floor between the buckets) and no matter what pump I have tried, they all have been loud until this one. Now my fan (4" vortec) and a breeze fan for the plants are the loudest things I have. The AP40 is so quite, it actually might make more noise with the bubbles than the pump. I have also noticed better root growth right after I put it in, my old pump could not run 6 5" round air stones, this one runs that many and 2 14" long stones for res and controller (water level)and I am only using 8 of the 12 ports for air. I found my on ebay for an awesome deal, It was less than 100 shipped.