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AETech ETS 800 Gemini Skimmer

Brand New ETS 800 Skimmer
Stable Foam Inside Skimmer
Skimmer in need of a cleaning
Beckett Injectors Installed in ETS Manifold

Beckett Injector Assembled

What is a Beckett Injector?

A Beckett Injector is a venturi. A venturi is a device that uses a change in pressure to draw in air into a water stream to create air bubbles. This is the Beckett Model 1408 Foam Jet Fountain Nozzle commonly used in Ponds. You can find it in the lawn & garden section of most Home Depots for about $15.

Pictured left I have taken the Beckett Injector apart so you can see how simple it is. Everything is made of plastic and it has no moving parts. The pointed arrow piece with the ball at the end creates the difference in pressure inside the beckett. Place that in the center of the two halves, then place the clip rings on either side to hold it together and the beckett is complete. The package also comes with a short pipe and a ½ inch thread to slip adapter.

Beckett Injector Assembled

Here the two beckett injectors have been assembled. The white PVC parts at the left end are male threaded nipple adapters which allow the injector to be attached to the ETS 800 manifold. The ETS 800 manifold uses ½ inch male threaded barbed reducer fittings as injectors. The two original injectors removed from the ETS can be seen at the bottom of the picture.

The beckett came with a thread to slip adapter but the supplied pipe is not a standard PVC or CPVC size so you need to use the adapter. That left me with two ½ inch female connections. I used a ½ inch male threaded nipple adapter to hold them together. One end threads into the ETS manifold, the other threads into the beckett adapter. Male Threaded Nipple Adapters tend to be hard to find. You might have to special order it, even so it should not cost more than about 50 cents. As pictured, each beckett assembly is about 6 inches in size.

Beckett Injectors Installed in ETS Manifold

This picture shows both beckett assemblies threaded into the ETS 800 manifold. This manifold sits on top of the ETS 800 dual mixing towers.

I first experimented with all of the bio-balls removed from each tower and I had very good results, however it was suggested that I add some of the bio-balls back into the mixing towers to help increase the contact time of the skimmer. I tried 8 balls in each chamber and then 10. The more you add the dryer the foam produced should be.

Beckett Injectors Modification

After a few days I started to get an annoying banging sound from inside the skimmer. It sounded like a bio-ball spinning in the mixing tower. However, after careful observation I determined it was not a bio-ball spinning. It turned out to be the beckett itself bouncing around inside its housing. The beckett has two small tabs that rest in slots on the housing walls.

So much pressure was being passed into the beckett that it started to rock back and forth like a church bell. I would hear 5 to 10 rapid bangs every second or so.

I removed the beckett and wrapped Teflon tape around each little tab to make the tabs larger. This took a little more effort to close the beckett housing but the beckett was firmly in place. When I fired up the skimmer the becketts remained completely silent.

ETS 800 air bubble size before beckett modification

Why convert the skimmer to Beckett?

Not everyone needs to do this. For most people a standard ETS works flawlessly. However, in the years I've had this ETS 800 I have never been happy with its performance. I could never get a small bubble size out of the skimmer. Upgrading the pump from a MAK4 to a Iwaki MD55RLT helped, but I was still unable to get the performance that other ETS owners did. As a last ditch effort, I decided to try this modification before tossing out the skimmer and getting a HSA or Aerofoamer skimmer (both use Beckett Injectors).

I saw pictures of someone who converted a ETS Reef Devil 3 to a beckett and I felt I could use that idea to convert my much larger ETS skimmer. I've since found people who have converted ETS 1000 and ETS 1200 skimmers also. Everyone I have talked to who has made the conversion is much happier with the skimmer after the conversion.

ETS 800 air bubble size after beckett conversion

This picture was taken 3 days after the modification, using the dual becketts as pictured above. I've been tweaking the design a bit and have gotten even smaller bubbles. I'll update this site with my new ideas once I'm happy with settings.

You can fine tune the bubble size by restricting how much air can reach the beckett. I've added a ¾ inch to 3/8 inch reducer on the air intake to the beckett chamber. I then added a 3/8 inch ball valve to restrict the flow of air reaching the beckett. I have future plans of putting the becketts inside air tight containment chamber like HSA and Aerofoamers skimmers use.

Who cares about bubble size?

Bubble size is the most important design aspect of a skimmer other than perhaps the contact time a bubble has with water. The bubble size determines a skimmer's efficiency because the bubble size determines the surface area available for proteins to stick to bubbles. The smaller the bubble the more surface area available due to the increased number of bubbles that can be placed in the same volume of space.

Keep in mind that these bubbles are at the base of the contact chamber in the ETS 800. The bubbles size inside the skimmer sump most likely are even smaller. However, the ETS 800 sump box is made of black acrylic and I can not observe the bubble size. I can only see the bubbles that have already merged, expanded, and started to rise. Other skimmers like the Aerofoamer and even new ETS skimmers like the Evolution series are all clear acrylic which allows for direct observation of the skimmers efficiency.

UPDATE 12/11/2001: After getting many questions on how to perform this modification I decided to update this page to let everyone know that I no longer use the beckett modification for an ETS skimmer. The gain of a smaller bubble size seems to be short lived. After a few months I switched back to the standard ETS injectors and it seemed to perform better than the beckett modification. I still feel beckett based skimmers perform better than downdraft skimmers, I'm only saying that converting an ETS skimmer to use a beckett is not worth the trouble.

A beckett based skimmer has several key design differences from a ETS skimmer. These differences are key to getting good performance from a beckett injector.

  1. First off the beckett must be used in an airtight containment chamber that the air valve is connected to. The beckett needs to be operated under a vacuum like condition within the containment chamber.
  2. Secondly, the chamber needs to be large enough to hold the water spitting out of the vent holes of the beckett and yet not drown the beckett injectors.
  3. Third, the output of the beckett needs to be submerged in the sump of the skimmer. This is the only way to keep the microbubbles suspended in water. You will notice every beckett skimmer has the injector directly connected to the skimmer sump or connected via a tube to the base of the skimmer sump. The wide downdraft tube of an ETS skimmer is just not ideal.

If you want the performance of a beckett skimmer, get a beckett skimmer -- that's what I did.