I decided to go with a Mazzei Injector (Fancy, top of the line Venturi injector) skimmer.  The main reasons were these are suppose to produce the finest bubbles of any Venturi injector, and that I wouldn't need a huge pump, so I could get fairly good efficiency.  The overall project has turned out very good! And now this is one of the most popular articles on my website!

Why do I need a protein skimmer?: Skimming is one of the most important parts of keeping a healthy successful reef aquarium. Many people get all worried about how they are going to light their aquarium, and sometimes water flow, but filtration is a huge part of the equation. How are you going to filter out nutrients, what kind of Live rock, or sand bed are you going to use are just as important! A good protein skimmer for your reef has to be quiet, efficient, consistent, and remove lots and lots of stinky, smelly gunk.

1. Design of the skimmer

Theres a few things I looked at when designing my skimmer. I wanted a compact skimmer that was cheap to build, and that included the price of the pump.

Recently beckett or spray induction skimmers have been hot, so has the the new DIY eductor style skimmer.  These required aquarium pumps that would've been as large as the return pump on my reef tank so i thought they were a little overkill.

Lifereef and Euro-Reef both have excellent skimmer designs from what I've heard and seen, and I also heard about this wonderful device called a Mazzei Injector.  Its basicaly a super venturi valve.  They are the best you can get.

I decided to go with the venturi design.  There was a few basic variations of the venturi.  My girlfriend happened to be sick in the hospital at the time I started, so I had many long hours while sitting there to go through different designs on my head.  I finaly decided on a injection from the top, angled down and a bit off center to create a downward swirl.  I knew I didnt want a cyclone effect like some cheap venturi skimmers, as I've seen some expensive skimmers in action and they have a wonderful almost random swirl to the bubbles in their reaction chambers.  IMO a cyclone wouldn't let the bubbles do their thing.

I decided the water would exit from the very bottom, so I'd have my water flowing down, but of course bubbles going up.  This would give me my counter current design.  If it worked well and I could lower the height of the water in the chamber this would also give me extra bubbles because the spray would hit the water instead of being injected under water. It would also put less back pressure on the mazzei creating even more bubbles.

The water-air mixture starts out on the same path, but as they rise, the water starts to seperate from the bubbles. While the bubbles try and push each other up the neck, the water is forced to return down mixing with more air, and producing the counter current effect. The water eventualy exits at the bottom, while the seperated organics are pushed to the colleciton cup.

The rest is just basic skimmer design. A neck and collection cup.