Skimmer Mod help

I have a no name skimmer that I did some mods to. first I cut the neck from the main cylinder to the collection cup by about an inch. second I added a air stone. my question for everyone is 1. does the blue air stone work as good as the wood (dont know whats it called). 2. how much skimmate should a 75 gallon tank with 3 fish and LR be producing? it has a lot of foam at the top but the cup doesnt seem to have a lot collecting yet.

 

For skimming, only the wood ones make fine enough bubbles to be effective in the skimmer. The blue stones, work well enough for aeration...