Ok i just got my euro-reef rs 135 in the mail today and I must amit i have no idea how this thing works, and there is no set up instructions.

I am still in the VERY early stages of setting up my tank.

so is set my sump on my kitchen counter and put some freshwater in, i placed the skimmer in and plugged it in.

it made some bubbles but no where near the amount of what i have seen in pictures.

i played with the air intake tube valve and the foam adjustment pipe but no real luck.

whats going on?
how deep should the skimmer be in the sump?
How high up should the water level be inside the skimmer?

Your first problem is you weren't using saltwater. Fresh water will not create micro bubbles like saltwater (this is the reason they don't use protein skimmers on freshwater). You could add some vinegar to the water and that will help you see some foam if you don't have saltwater.

I've got the same skimmer. It works nicely... although I wish the collection cup was bigger.

According to the people who make them, you want to keep it in about 6 to 10 inches of water for optimal performance. I don't really pay much attention to that... right now mine is prolly in a foot of water in my sump and its working just fine.

PSH is right about the saltwater thing. Freshwater doesn't bubble up in the skimmer like saltwater will, so if you want to test it out, test it with salt water (or you could try adding vinnegar... and then your house will smell like vinnegar for a day).

So... to set it up, you stick the powerhead on it (which I'm guessing you figured out), and pull the postfilter tube (where the water ends up coming out of the skimmer) all the way down. The postfilter tube lets you adjust how much water is actually in the skimmer body. The higher up you put the tube, the more water. You want to start it as low as it can go, and even then you might have your collection cup filling with clear water for a few days. Just let it run and overflow the collection cup until the water settles down if that happens.

Basically thats it... it's not too complicated. Water and air go into it, make an awsome little bubble storm, and the collection cup smells like fish poop after a few days.