adjustin skimmer. please help

[mistermismatch]

so i built my own skimmer a few weeks ago and ive been battling with it to get it set up. i have it set up in a bucket now to test it. i usually set it up so that the foam bubbles into the cup every once in a while. i get a thick sludge around the cup and a slightly lighter liquid in the cup which settles to the bottom. ive "dirtied" the bucket water by squeezing a dirty filter sock into it. it always seems to work for a few hours and eventually dies down untill all i see is small bubbles below the neck. the pump im using is from an old broken venturi skimmer i had. ive adjusted water flow by drilling holes in the intake pipe under the water level. my air pump is adjustable and rated for 26-212g tanks.its the biggest "petco" brand one avail.

ive measured the waterflow rate and calculated it at 2.4 gph

problem: the skimmer dies out after a few hours. ive let it run for a day and a half and the bubbles never build back up. help????

 

[melosu58]

Moved to General Hardware and equipment discussion.