air powered skimmer

[Invigor]

just looking from some tips to fine tune this thing. It's producing a nice green skimmate but I still think it could be a "dryer" foam. Any ideas? I've 'got it hooked up to a gang valve so I can control the airstone and the water it's pulling through.

It's a counter current skimmer. I put a limewood airstone in it instead of the "stock" one...what a difference.

From reading I hear the trick is to replace the airstone every month.

TIA.

I'm not looking for responses such as "you dumbass, buy a better one." so please withstand your inner voices telling you to say that.