Redeyereef,
Could you tell me your real name? I mean I've heard so much about you, but don't know your real name. Haha.
Anyways, got some prelim. numbers back from Brent. The airtech 40 pump puts out a solid 78 SCFH through (2) 6" fine pore diffusers at about 20" of water over them, which is about the normal functioning range of two properly driven becketts. I'm not sure about the bubble size yet as Brent has not tested it in clear acrylic tubing yet, but a good sign was that he couldn't see a thing in the tank he was testing. Hehe. I think he may do a little more testing with different sized airline or at least I'll suggest that to him.
Theoretically, with the airtech 80, you would be getting twice of that through 4 6" stones so in essence, like 4 becketts fully driven on your skimmer, which I don't think your skimmer could handle. I think the airtech 40 would be just perfect for your skimmer if you decide to retrofit that sucker. Honestly, I'm afraid the airtech 40 may be too much as we aren't just talking about pure air injection... we're possibly talking about air injection with extremely small bubbles, smaller than needlewheels and normally driven beckett skimmers. I'm very interested to see what Brent thinks about the size of the bubbles when he puts the stone in a clear acrylic tubing. You are more than welcome to borrow the airtech 40 for the time being to give it test run if you want after Brent is done running the numbers. The smaller the bubble, generally the more stable the foam head is in general, so you would need less bubbles to achieve similar levels of skimming when compared to other forms of air injection.
I think that Mike has discovered this for himself. He gets an incredibly tall and stable foam head because of the size characteristic as well as the volume of bubbles he is injecting.
Peace,
John H.