The best way to tune your Protein Skimmer: Learn how in just 5-minutes!

Today we show you how to tune your protein skimmer for peak performance. Not just collecting the most waste and cleaning the tank but doing it in a stable manner with as few adjustments as possible.


The challenge with tuning protein skimmers is they actually come with very little information on how to use them effectively and fail to define the factors that affect performance. How do you know if your skimmer is working at peak performance? It is not just about making foam, it is creating the right kind of foam to match your tanks waste level.


Skimz Internal Kone Skimmer


For decades we have all been told that more air is better and the best way to tune wet vs dry skimming is to adjust the water level via the outlet pipe or skimmer drain. Those two statements are just a small part of the overall picture and most of us have been overlooking some pretty obvious performance and tuning factors.


A good way to understand skimmer operation is like a foam engine designed to produce and collect organic laden foam. Most of you are familiar with a standard combustion engine that mixes air or oxygen and fuel in a controlled reaction chamber to create a desired burst of energy. A skimmer is very similar in that we are mixing air and organic waste laden saltwater (the fuel) to produce a stable foam head inside a controlled reaction chamber being the skimmer body and neck.


Internal Protein Skimmers


Whether you are talking about a car’s engine or a protein skimmer, real tuning is about adjusting the air to fuel ratio for optimal performance. With a combustion engine, if you add too much fuel it’s called running rich which will dirty the engine and reduce performance. Too rich and you can flood the engine to the point it will no longer work. The flip side of that with too little fuel is called running lean which can produce inconsistent performance and frequent stall outs.


The same thing will happen with a protein skimmer so we are going to use the same exact terms. Running rich would be high waste levels and not enough air while running lean would be low waste levels and too much air. Once you know what to look for in your protein skimmer, the signs are obvious


Running Rich


Running Rich

Since fish waste and uneaten food the fuel, running a skimmer rich means a higher waste level in your water. Test results with high nitrates and phosphate levels will indicate this. Too much fuel or waste and not enough air will result in dirty brown foam that slowly rises, often has visible chunks in it and collects a ton of gunk inside the skimmer cylinder or neck. Most of the foam fails to rise and very little foam finds its way into the collection cup.


In this case, cleaning and removing the brown paste from inside the skimmer’s neck can still be an effective way to export organics from the tank but the foam engine is obviously running less than optimally or too rich.


Running Lean


Running Lean

When a skimmer is running lean there is not enough organics for the amount of air and a sure fire sign of an oversized skimmer. The foam will be milky white from top to bottom and rising considerably fast. Rather than collecting organic laden foam it is more akin to a boiling pot of water where a majority of the bubbles burst immediately at the top of the foam head as opposed to gently overflowing into the cup. You won't see chunks in the foam or muddy buildup inside the skimmer neck either.


In this case, there is not enough organics in the tank water to keep those bubbles intact and you end up with fragile bubbles. The high velocity of air leaving the skimmer neck causes all the bubbles to pop before they can form a stable foam head. This is also the condition that causes the random overflows.


Overflowing the cup will happen typically hours after a feeding when the uneaten food has had a chance to break down in the water, increasing the fuel, and causing the bubbles that were previously popping to stay intact. The cup quickly fills with mostly saltwater and eventually overflows out into your sump or worse yet onto the floor.


Outlet pipe adjustment gate valve


Determine Skimmer Performance

Adjusting the amount of air going into the skimmer pump is the best way to really dial in your skimmer for consistent performance. First, you need to determine whether your skimmer is running rich or running lean.


Optimal skimmer foam head


When operating optimally your skimmer will form a thick slow rising foam head. The foam head will maintain its shape and often slightly discolored. You should not be getting a whole ton of buildup inside the skimmer neck either. If you feel your skimmer is not performing optimally, follow these steps to determine your situation so you can then take appropriate action.


  • Sump water level: First, make sure you installed the skimmer within the recommended water height. This matters because water height changes back pressure or head pressure and therefore pump performance. We found these effects to be most dramatic on smaller skimmers and lower wattage pumps.
  • Skimmer water level: From that point, use the gate valve or riser tube to collect the foam as best the skimmer can with the factory air draw or “right out of the box”. Start with the top of the foam head somewhere close to where the cup meets the body and then go up or down in small increments as necessary. Remember to give it a few hours in between the adjustments.
  • Observe: Over the next few weeks you will notice signs of whether or not your skimmer is running lean or rich. Remember mud on the walls (rich) or boiling pot of water (lean).

How To Increase Air Draw

If you see the signs of running rich this means your running with higher organic levels and need more air inside the protein skimmer to get a stable foam head and collection.


Clean venturi


Before anything, double check that your venturi and airline are not clogged as well as keep your pump clean and in good working condition. These venturi fittings have a tendency to clog with salt or calcium, sometimes as quickly as every few weeks. Just use freshwater and clean it out with a tiny bottle brush.


When using an AC pump driven skimmer, you can simply raise the water level in your sump one inch at a time. Allow a few hours for the skimmer to settle in between changes and evaluate again. By raising the water height in your sump you are effectively reducing head pressure which increases the amount of air the pump can draw. This is especially effective on smaller skimmers and lower wattage pumps.


External Protein Skimmers


DC pump driven skimmers give you the ability to adjust the speed of the pump and increasing the pump speed will increase the air draw at the same time.


  • Increase pump speed on step at a time using electronic pump controller.
  • Adjust the foam height inside the skimmer to the best of your ability with the gate valve or outlet pipe.
  • Let it settle for a few hours and evaluate performance, repeat the process as necessary until a stable foam head is achieved.

If you eventually reach your limits of maximum water height in the sump and maximum pump speed yet still feel your skimmer is running rich, you simply have a skimmer that is undersized for your organic input. As long as nitrate and phosphate are not continually rising or out of control, you don’t necessarily have to replace the skimmer but you certainly know what to look for when upgrading your tank. Bigger pump with more air and preferably an option to adjust that air input with a DC pump. Recirculating DC protein skimmers are going to offer the best range and precision, even better than internal single pump DC skimmers.


Optimal protein skimmer performance


How To Decrease Air Draw

Running lean, meaning not enough organics or too much air for your organic load is something entirely different. This is much easier to adjust and likely a much more common tuning challenge with today’s high powered protein skimmers.


The signs of running lean are a ton of bubbles, rapidly rising that burst at the top like a boiling pot of water. In this case you need to reduce the amount of air injected into the skimmer. The primary benefit of reducing the air injection is the bubbles will rise slower. Fewer of them will pop prematurely and you will start to produce a thick foam head which results in the most efficient collection or waste removal.


First things first, double check for any clogs in the venturi and that your pump is in clean working order. You can then reduce the air draw by lowering the sump water lev el around the skimmer which increases head pressure on the skimmer pump.


Using a ball valve for air adjustment


You can also put a ball valve on the venturi air line to choke back the amount of air that is sucked into the pump. A common way to do that is a 3/8” Murlok Ball Valve and two Stem x Barb Adaptors.


It is important to understand that when you turn down the air using either of these methods, you will also increase water flow through the skimmer so this only works to a point. Somewhere around a 50% reduction in air will start to cause problems in the overall function of the skimmer. This will be obvious because of a severe case of microbubbles leaving the skimmer and generally unstable performance.


VarioS DC pump speed adjustment


Finally the best and most precise way to dial in the skimmer is via a controllable DC water pump. If you have a DC protein skimmer, you can slow down the water flow and air draw at the same time.


  • Drop pump speed one step at a time
  • Adjust the foam height inside the skimmer to the best of your ability with the gate valve or outlet pipe.
  • Let it settle for a few hours and evaluate performance, repeating the process until you consistently collection with a stable foam head.

In any case, once the air to organic ratio is optimized, a nice stable foam head that maintains shape and rises gently will occur.



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