Protein Skimmers

Protein Skimmers


Good water quality is an essential requirement for happy, healthy marine life and providing this needs to be your number one priority at all times.


Keeping on top of water quality is the single best thing you can do to avoid problems with your marine aquarium full stop.


After biological filtration, the next most important aspect in maintaining good water quality is physical filtration done by protein skimmers (a.k.a. foam fractionators).


This process gets rid of dissolved organic wastes in the form of protein and amino acids before they breakdown and are converted to the toxic compounds ammonia and ammonium.


These waste products are anything organic from uneaten food to fish excrement, detritus, decaying marine organisms. It all breaks down into the same substances by the work of microscopic bacteria.


The protein skimming process removes undesirable dissolved nitrogenous waste at the source and greatly reduces the load on biological filtration microbes. This means fewer nitrates are being produced in the system and the water is more stable – a very good thing!


Other than protein, skimmers also remove fats and fatty acids, carbohydrates and trace elements such as copper and important iodine (which will need to be topped up in reef aquariums). Contrary to popular belief skimmers do not remove plankton because they are simply too big.


Your protein skimmer also serves to oxygenate the water, reduce algae growth, increase water clarity and increase its reduction/oxidization potential all of which are also highly beneficial for our marine life.


This waste material accumulates at the waters surface as protein is attracted to air and away from water (hydrophobic).  Protein skimmers work because dissolved organic molecules stick to air bubbles and then rise to the surface of the skimmers reactor chamber to be trapped and separated from the rest of the aquarium water.


This residual foam should reduce into about a cup a day of smelly brown liquid, which you most definitely will be glad has left your aquarium water!


It deserves a mention right here and now that you cannot skim an aquarium too much, protein skimmers should run constantly and if your aquarium is quite big you should have two – these things really are worth their weight in gold.


The process of protein skimming also occurs in the ocean with the natural wave action over reef environments creating sea foam that deposits proteinacious waste on the shore.


I strongly recommend any marine aquarium owner to purchase a good quality high capacity skimmer; the best you can afford. This is an investment in the health and well being of your marine fish and invertebrates. These wonderful devices are an absolute must for every saltwater aquarium there is nothing better that improves water quality.


Protein skimmers can be inside aquarium, hang-on back or in sump models. Hang on and in sump options are the best in my opinion. Water fed from the very surface of the saltwater aquarium is more desirable as this is where most dissolved waste will accumulate.


In sump models should be able to catch all water from the aquarium, ideally from a surface overflow box first before any other water processing takes place (such as mechanical filtration) to be most effective. They should sit in a contained area with a constant water level (reduces stress on skimmer parts) in a sump within a sump so to speak; this keeps the unskimmed water from flowing to other areas of the sump allowing the most effective water filtration route possible.



So what makes a good skimmer?

⪼The flow rate/turnover of the skimmer pump (gallons per hour) should be around 5 times the tank volume as a general rule; you want a high volume of water processed.

⪼The finer the bubbles produced the better as efficiency is all about surface area and small bubbles have more surface area in the reaction chamber than big ones (because there are much more of them!) so more waste is removed.

⪼A longer contact time between water and bubbles increases efficiency as well, so a larger skimmer works better than a smaller one.

⪼You also want a lot of consistently small bubbles with the right water to air ratio for maximum waste removal efficiency.


When you first set up a skimmer you may need to tweak the air/water volumes to produce the best efficiency possible for your system.  Do this by keeping one constant and adjusting the other.  You’ll be able to tell when you’ve got it right by the appearance of your skimmate which should be dark brown and about a cup per day.


Different types of protein skimmers


Counter-current skimmers

More efficient than co-current (water and bubbles flowing in the same direction: the earliest models) skimmers because with counter-current models there is a longer reaction time between bubbles and water because the water has to flow down through the upward stream of bubbles then back up, which means more waste is removed because of increased contact or “dwell” time.


Co-current skimmers

The earliest and most simple skimmer types; co-current, air driven skimmers also use lime wood air diffusers (which decay and block up with time so need to be replaced) to produce bubbles. Years later the Venturi valve was invented to draw in air from the output side of the water pump then injects both the water and air as a high pressure whooshing, foaming mass into the reaction chamber which also increases air-water contact time, efficiency and output. This model type does away the need for an airstone or air diffuser and gives better efficiency for less cost as co-current air driven, however there are quite a few ineffective models on the market to beware of.


Aspirating skimmers

An alternative to the Venturi design is the aspirating skimmer, which pulls in air and water together from the water pump intake side then “chops” it up using an impellor such as the “needle wheel” design to create much finer bubbles to be injected into the reaction chamber, again increasing efficiency and contact time. These types of protein skimmers are typically very efficient, consistent performers and take up relatively little space compared to the other types, the best models are not cheap but require little maintenance and perform fantastically, especially the “needle-wheel” models.


Downdraft or environmental tower skimmers

Another relatively new protein skimmer innovation is the downdraft skimmer or ETS (environmental tower skimmer). This type of skimmer uses a long tube that connects to the sump down which water is forced by a large pump down over bio-balls which diffuse the water violently and turn it into a foam where it enters the sump and is collected after a long dwell time. These skimmers are big, expensive to purchase and operate and are especially good for larger aquariums.


Cone skimmers

One of the newest protein skimmer forms to emerge is the cone skimmer, this conical body shape allows for a more effective accumulation of protein-rich foam with reduced turbulence and massive efficiency benefits.



A protein skimmer is a very valuable addition to your marine aquarium and you should buy the best you can afford and clean it out regularly (the reaction chamber neck, collection vessel and air injecting unit especially).


A high efficiency, large capacity skimmer that is easy to clean and adjust is a good skimmer. The best protein skimmers are reliable and require little maintenance and adjustment they should serve your marine life well for years to come.