Skimmer

You may know more about this than I do, but what I did was take the bioballs out.  I think they do better on FW systems and can cause nitrate issues in SW.  I am not familiar with that skimmer but that is a monster pump for a skimmer.  How big is your tank? I have a ASM G-2 with sedra 350  mod for my 90g and it works great.  I then have an ASM G-3 with sedra 500 w/o mod on another 90g and it works great.  You want it to pull tons of skimage out of the water, if I underestand your post correctly you are not wanting it to?  As far as the micro bubbles you may want to investigate doing a mod. I found that it made a huge difference, several people here have done mods and there is a thread on how to do them as well. 

I would love a mod, but the only mod I have found for a downdraft is a durso and the articles I have read seem to think it doesn't help much.

The downdraft has to have the bioballs they are what breaks up the air, If you are running 4' of feedline to the skimmer and its smaller diameter you are greatly reducing its output, if its rated at 600-900 and you are pushing a mag 7 up four feet through restricted tubing you are lucky if you are even at 500 gph or so, they aren't particulary good at head pressure.  First thing I would do is use larger diameter hose going from the pump to the skimmer, and try to cut down the distance if at all possibly, that should make a huge improvement.  OTherwise stay on the lookout for a mag 9 or equivelant.  Downdrafts are pretty simple, pressurized water, simple venturi and bioballs to break up the bubbles.

I took the bio balls out of mine on advice of others in the group.  My skimmer is working much better now and I have to dump the collection cup once a week.  It is pretty gross what comes out of it.

well here is another question...not to hijack the post or anything. but i have had a skimmer on my 90 since the day i set it up, well i have had a skimmer in my water since feb...i have moved tanks several times. but anyway it skimmed for the first few days and then hasnt skimmed anything since, i recently took it off cause i was considering mod it but decided not to anyway it was off for about 2 weeks then put back on and is skimming decent right now as for the past week, i feel that it will stop skimming here in the next few days as it is slowing down. so is my skimmer to big for my tank or do i not have enough stuff in it to dirty the water fast enough for the skimmer?