Anyone experienced with Downdraft type Skimmers?

I just cant seem to find much about these things which surprises me. The problem Im having is it goes through phases where it doesnt collect tiny bubbles in the reaction chamber. It seems even in the bio ball tube the bubbles are large. What I also dont get is why right after I feed my tank rotifers and oyster eggs it suddenly starts doing that lrage bubble business. With my other skimmer (Berlin XL) it would do the opposite, overflow with tiny bubbles. Ive checked and cleaned the air inlet twice so I cant see that being the problem. I must admit im still a little uncertain of how this thing works. I know the water injected onto the bio ball tower pulls in air through the venturi. If this wasnt a custom made skimmer I could call the company and ask them. If this doesnt work im gonna have to call ETS or someone who makes downdrafts and tell them I have one of theirs. Below are a list of questions, if anyone knows the answers please feel free to take a stab.

Does the amount of bio balls in tower make a difference? The tower is a little over 4 feet. Right now I have about 6-8 inches of empty space between top bio ball and injector. I tried to stagger the column of bio balls as best i could but there are certain series of balls that are stacked in a single file, like not offset. not sure if that makes a difference.

Could the pump not be strong enough? I just bought a Coralife High PRessure 790-P Inline pump. At the 5 feet of head pressure its still blasting 700 gal per hour.

I was about to ask if it could just be that I removed almost all the organics there are in the tank and theres nothing for the water and air to react with. But it wouldnt makes sense that it consistenly stops producing foam immediately after I add organics in (oyster eggs, rotis). Besides, an hour before I added the foods the skimmer looked like it was performing properly. There was about 12-16 inches of accumulating bubbles. It was very dense and organized with larger bubbles in the first 2-4 inches with tiny ones on top that eventually gave way to a foam you could scoop out with your hand in a clump and apply it to your face like shaving cream. Again tho, i add the food and suddenly the opaque white chamber changes to watery violent boiling.

So what the heck is goin on

 

Nevermind guys heh. Its working great again and it might have somehting to do with the lid. I put it on and wallah, procusing great foam. Will see what happens tomorrow when I feed again this time with the lid on.

 

Yea it turns out theres a reason for this happening. The bubbles turn from tiny to large because of oils that can either come from your hand or from food. Im kind of surprised it took so long to figure out why this was happening, I had to actually call ETS and pretend I had one of thier skimmers. So it seems in order to not have this happen i cant ever feed my tank or put my hands in the tank. Something just doesnt sound right about that. There must be a way to prevent this reoccurant "break in" period. Would adding prefilters help? If no one knows Ill place another call to ETS.

Basically how can I feed my tank without disturbing the bubble size in the reaction chamber?