Ted, I have the ALA6GL diffusers on my system. There isn’t a check valve on the airstones. On my blower there is an air filter on the intake side but not on the output. So I probably am getting dust from the vanes in my airstones. I just replaced the graphite vanes last month although the old ones were only wore down about a third after a year of operation. I have a bypass valve on my compressor that allows me to blow off excess air, my one diffuser is bubbling to beat the band but I’m not putting all of the air to it. I had planned to clean/replace the airstones when the water warmed up a little bit. Bill Cody mentioned the membrane type air diffusers, I have a Koi pond that is slightly over 60,000 gallons and I use these. They are built into the domes that cover the four bottom drains. They seem to work very well, do you have a preference? They do seem to be less maintenance, from what I understand if they start to get clogged all I have to do to clean them is to crank up the air and that will expand them enough to unclog them. Thanks for your help, Joe.
