Re: sweetwater stones
A couple weeks back I thought I'd give the mist method a shot and ordered several Sweetwater stones from AES. I only tried one of them, but it certainly didn't produce a mist of tiny bubbles the size of a period. Most were rather large (though probably smaller than a regular airstone), and floated rapidly to the surface even when placed in front of a vertical spraybar. Overall, it sounds pretty much the same as Cornhusker described.
I double checked the order receipt and what I ordered was AS10 = Fine-Pore Diffusers for Ozone and Pure Oxygen, 3/16" OD, ABS, 1.5" x .5". They look just like TW's picture.
The main thing that got me was the increase in CO2 expenditure required to get any sort of "mist" going. Normally I run about a bubble a second through my canister, but with the SW stone I had to crank the flow up until bubbles were just ripping through the counter. I never did let it all stabilize so I really don't know where the flow rate would have ended up when the pH was set. I just packed it in and went back to my original setup.
Is it possible we're doing something wrong? Normally, I've got the pressure regulator set to around 12-15 lb and the needle valve nearly closed in order to achieve 1 bubble/sec. With the SW stone, the regulator was the same but I opened the needle valve quite a lot.