[sasquatch]

the important factors in skimming are as noted by Nativevaman plus the other big one, volume of water pumped thru the skimmer, a skimmer that depends on a NW pump to supply both flow thru and bubbles is a bare bones skimmer and very limited in adjustment, a recirc skimmer with separate feed pump is far more efficient as the air can be adjusted up and down for wet/dry skimming and the feed pump can be sized properly for system turnover of 2x a day