Ok so I have an old Reed Dynamics INS 135 S Skimmer for tanks up to 250. Its running in a 29 gallon sump on a 120 gallon aquarium. I started running it last year in the winter. Maybe even the Fall. The pump it came with had seized and i found a brand new Rio 2100 pump that I installed the old venturi on. After some break in time it skimmed pretty well. Had to be emptied weekly. Recently within the past month or two it has just quit making skimmate. It has been getting less and less productive. Now it barely makes foam at all. I can adjust the air valve on the venturi but it doesn't bring it back to skim. I took the whole pump out after this was foing on for awhile and I soaked it in vineager for almost 24 hours in case calcium built up in the venturi. The pump is almost new. And this all worked well for quite a few months. I cannot get it to kick back into skim gear. The water level of the sump is the same. It could be possible that my tank water is too clean for the skimmer to work. That is actually all I can find that makes any sense. Would to heavy duty power filters be able to out compete a protein skimmer drom making any skim? I am not sold on that but its starting to seem to be true. Now I am just running it daily without it even foaming into the neck. Could my tank have reached a place where the bio filter is so good the skmmer doesn't work? Just two weeks ago it was barely reaching the skim cup for a few day. Then it slowly went to just making foam into the neck. Now it barely foams at all. The power filters habe been on the tank since before the skimmer. Nothing has changed with my setup.