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My original plans were to use ceramic airstones (diffusers) instead of a needle wheel pump, but I gave in to the needle wheel skimmer craze that was spreading through the hobby at the time. I ended up building the 6' tall DIY protein skimmer. The DIY skimmer performed very well but I ended up looking back the entire time, sure that I made a mistake in deciding not to build the counter current airstone skimmer. 

Back to the Drawing Board  

While the design worked well, I had a hard time keeping the needle wheel pump(s) operating. The Ocean Runner 3700 needle wheel pump lasted a little over a year but never performed as I had hoped. The pump was incapable of reliably handling more than 20 SCFH of force fed air. The Ocean Runner also suffered from inconsistant starts and would sometimes chatter for several minutes before it would finaly start spinning. I replaced the Ocean Runner 3700 with a Laguna 1500 motorblock fitted with a SWC (Salt Water Creatons) pinwheel wet end. The pump produced super fine bubbles but would quickly overheat and shut off. The overheating was likely due to a poor power factor resulting from an improperly sized needle wheel and/or volute.  

 I ended up retrofitting the recirculating needle wheel protein skimmer and transforming it into an airstone driven protein skimmer. To say the least, the performance of the transformed protein skimmer was inspiring. I immediately set out to redesign the skimmer from the ground up to enhance the efficiency and ease of maintenance. This project is the result of that redesign.

Design Goals

I spent a considerable amount of time thinking about how to create a skimmer that was easy to build (in a relative sense) and easy to maintain. I learned a lot from the initial protein skimmer build and subsuquent retrofit of that skimmer. While the initial design was modular, the actual components were hard to assemble and disassemble, mostly due to the fact that I used nylon thumbscrews.

The nylon thumbscrews were a nightmare! The nylon screws tends to stretch slighty when tightened, distorting the threads and making them hard to turn. The knurled texture is very hard on the fingers and causes severe discomfort and or blisters. I considered stainless thumbscrews for the new protein skimmer, but the cost was too high and I still don't like the idea of thumbscrews in general. The new skimmer will have stainless steel studs and wing nuts. As part of the initial retrofit, I replaced the nylong thumbscrews with stainless steel studs and wingnuts and am very pleased with the functionality. The wing nuts make it much easier to get the required torque on each flange section and are more gentle on the fingers. In a future desgin, I would like to incorporate a quick connect flange that seals via cammed v-groove clamp or similar device.

I cam up with a few ideas for maintaining or replacing the bubble diffusers without draining the skimmer. In the end, none of them were worth the effort to fabricate and implement. I decided to incorporate the diffuser manifold (see below) into its own flange. The manifold itself is constructed from several layers of PVC sheet stock that are machined to form internal passages for air and water. The diffuser manifold flange will simply stack against the body tube flange. 

Diffuser Manifold Plate

In the retrofit skimmer, I built a stand alone bubble diffuser manifold and lowered it into the skimmer body. The bubble diffuser manifold for this design will be similar but will be, in effect, a flange that is bolted to the skimmer body flange and base. It, like the retrofit bubble diffuser manifold, is comprised of several layers fo PVC sheet stock that are laminated together.

Body Flange

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