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Protein Skimmers – How About A Little Bubbly?

Equipment ReviewProtein Skimmers – How About A Little Bubbly?
By: Scott Zachow

To skim or not to skim? That has been a highly debated topic by many aquarist; both have factual reasoning behind their arguments. As with many other things in the hobby, people can be successful with and without skimmers; that is as long as there is an aggressive nutrient export program in place for those tanks that exclude them. We’re not here today to discuss which method is better as my mind is made up. Here we will talk about foam fractionation, how it works, what it actually does and review some forms of protein skimmers available today. Protein skimmers range in size and price from less than $100 to well into the $1000’s so there is one available for everyone; how effective they are is another story. The technique of protein skimming has been around for 8 decades for various industrial uses (Calfo, 2001) and became a notable piece of marine aquarium equipment in the late 1970’s in Europe; although many didn’t start classifying them as a “required” piece of equipment until later. For the marine aquarium, protein skimmers are devices that help to remove proteins and other organic material before they have a chance to become problematic.

A well performing beckett driven skimmer. The skimmate build-up on the walls of the riser tube is an indication that it is time to be cleaned. Photo Courtesy of Gene Schwartz.

At one time or another, all marine hobbyists have encountered a problem with Nitrates. Protein Skimmers do not remove Nitrates however they remove the organic material that otherwise has to be processed by the biological filter and therefore indirectly contribute to lower Nitrates. This is the reason that people recommend their usage. The process of nitrification is the conversion of marine waste to ammonia (NO), then to nitrite (NO2) and finally nitrate (NO3). Our biological filters (bacteria colonies within liverock or artificial substrates) are very efficient at these conversions but we are often left with the factor of nitrates to battle. Protein skimmers, by removing the same waste that our biological filters process, reduce the burden on the natural filters and reduce the amount of organic material that would be left as nitrates without it’s export. The argument can be made that while removing the organic material the protein skimmer is also removing useful elements from the saltwater. While this is probably true, the benefit far outweighs the downside especially since these same elements are being replaced through additions of trace elements and/or regular water changes. In addition to the benefits on water quality, Protein Skimming also increases the oxgen level in the tank and redox potential; both important and often overlooked aspects of water quality.

The way foam fractionation works is pretty simple. Organic matter within the water, proteins, amino and even elements that may be desired, are attracted to the fine bubbles produced by the protein skimmer. The organic material attaches to the bubbles, which forms foam that moves up the skimmer and into the collection cup. The product that is collected in the cup is referred to as “skimmate” and must be removed from the skimmer frequently. Obviously, it is very important to make sure that the material collected in the cup is not accidentally dumped into the tank. To ensure this doesn’t happen, it is best to use a skimmer that has a barb from the collection cup that allows you to drain the waste away from the water. The skimmate that is collected in the cup can vary from lightly colored and very watery to very dark and thick product that is nothing more than dark brown foam. Skimmers that produce different sized bubbles and that have different adjustments will produce different consistencies of skimmate. The best setting for any skimmer is one that will allow the skimmer to produce copious amounts of product and needs to be emptied a couple of times each week.

Sometimes when putting a new skimmer in operation, it may not produce skimmate immediately. This is nothing to worry about, as it will eventually produce once the skimmer “breaks in”. This period is needed to build a coating on the skimmer walls that will help the foam move up the skimmer and into the collection cup. You may also observe the skimmer ceasing to foam when certain foods or food supplements are added to the system, Selcon for example, and just the opposite when others are added. When liquid forms of food are added to a tank, DT’s Phytoplankton for example, it might be a good choice to turn the skimmer off for an hour or so to give the food a chance to circulate throughout the tank without being removed by the skimmer. Some water conditioners that have colloids will boost the skimmer performance to the point of over production so caution must be used at those times (although there is no need to add these types of conditioners to the water as long as filtered water is being used, just a cautionary statement).

The authors My Reef Creations MR-1 just minutes after it was set-up. Notice that the bubbles are very low in the riser tube and remained this way 2 days as the coating built up on the walls of the riser tube.

The skimmer can also have reduced efficiency when there is too much waste collected in the riser tube. To keep skimmers performing optimally they should be cleaned very often, weekly at least. This includes the riser tube, the pump to keep maximum amounts of water flowing through the device and the collection cup. No cleaners are necessary when performing this type of cleaning. Simply use hot water and paper towels to remove the scum that accumulates. Again after performing this cleaning you may noticed decreased or no skimmate from the device for a short period of time until the coating develops on the riser tube walls again. For this reason, some people recommend the use of 2 or more skimmers on their systems although this is out of the budget and space available for most aquarist.

It’s a dirty job but someone has to do it. Here a skimmer is totally dismantled for a good thorough cleaning which is necessary to keep it performing optimally.

Here are the key things to look for when selecting a skimmer for your tank. When looking for a skimmer look for one that produces a large quantity of very fine bubbles. More bubbles of a smaller size have more surface area for organics to attach to and therefore is recommended over fewer, larger bubbles. Get a skimmer that has a high flow through rate but yet has long contact time. The more water passing through the skimmer with optimized contact time for the organics to attach to the bubbles, the better. Be sure to get one that is rated for 2x – 3x more than your current tank volume. I don’t think there is a such thing as over-skimming so getting one oversized will allow you to rest easy knowing it is capable of reducing the strain on your biological filter and will also provide potential uses for larger aquariums, since we’re always wanting to upgrade to a larger tank. Next make sure to get one that is easy to clean and if possible has a barb in the collection cup for a hose to attach to. It is much easier to allow the product from a skimmer to drain into a larger container that can quickly be removed and dumped without interfering with the skimmer operation. Get a skimmer that is known to produce well. There are a lot of skimmers on the market that appear to have the right price, but the performance leaves a lot to be desired. The small inexpensive skimmers driven by air stones and no pumps are literally useless. Lastly get a skimmer manufactured by a reputable company, one that offers replacement parts if needed and provides solid support when queries are sent.

There are many, many types of skimmers available on the market today and some different technologies that they use. As just mentioned, with today’s technology air stone skimmers are pretty much a waste of money. The bubble production isn’t that great and it quickly deteriorates, as the wooden air stones get dirty and clogged. Remember with skimmers, the more fine bubbles the skimmer produces the better. If you happen to have one of these skimmers I would recommend looking for an alternative solution. If your stuck with it, make sure you diligently clean and replace the air stones for best performance.

Venturi skimmers aren’t bad devices. The pumps that push water into them have airlines attached to them so as water is pushed into the skimmer air is drawn in and produces the bubbles for the skimmer. They aren’t the most efficient but they can work well. Lifereef uses Venturi skimmers in their high quality sump systems.

Needle wheel skimmers use a small device that chops an air-water combination from the pump into very fine bubbles. The amount and size of bubbles produced from needle wheel designs is impressive, especially for the low powered pumps that are required to operate them. The Aqua Medic Turboflotors are examples of needle wheel skimmers.

Spray Injection is a type of skimmer patented by AquaC. AquaC skimmers are high quality skimmers that perform very well. For a hang on skimmer, the Remora Pro utilizing the Spray Injection technology is hard to beat.

Beckett skimmers are also gaining in popularity; My Reef Creations is an example of this type of skimmer. High-powered pressure rated pumps push water though the Beckett injector and produce a large amount of very fine bubbles. These too are very effective skimmers and are highly recommended.

I would also suggest browsing the Internet for some cool DIY skimmer projects. People are always posting step-by-step instructions for these various types of skimmers and if you’re the handy person with the means to build your own, this may be a way to save a few bucks and still end up with a quality skimmer.

Reef On!
Scott Zachow

References Cited:

Calfo, A. 2001 Book Of Coral Propagation Vol. 1; 104-109.

Knop, D. 1996. Giant Clams: A Comprehensive Guide to the Identification and Care of Tridacna Clams; 138.

Fossa, S. and Nilsen, A. 1996. The Modern Coral Reef Aquarium Vol. 1; 258-261

Fenner, R. 2001. The Conscientious Marine Aquarist; 83-85.