Protein Skimmers

Protein Skimmers

One of the most desirable and in many cases indispensable pieces of marine equipment are Protein Skimmers.

Called foam fractioners among the science folk, skimmers have been available since the early days of the serious marine aquarium hobby.

Benefits of Protein Skimmers are many. First, their purpose is to remove dissolve organics from your tank water before they decay and cause your water quality to decline. Skimmers work by mixing air with the marine water, generating bubbles. The dissolved organics stick to the interface between the bubbles and the water. The bubbles burst at the top of the unit, and the organics fall into a collection cup there.

The skimmer cup fills with what is called the skimmate. The smell of the skimmate will bring great peace of mind that is out of your tank water. Many have to empty the skimmer cup daily, some more lightly stocked reefs every other day.

Emptying involves rinsing the cup out under a running tap, then replacing it on the unit. Also, one should clean the biofilm that forms inside the skimmer every few months, gaging the time based on the amount of biofilm, since it can hamper the skimmer’s filtering capabilities.

Better Skimmers generate many tens of thousands to millions of very tiny bubbles, usually mixing the air and water through some type of valve. Many methods of mixing the air and water are patented by the manufacturer. The smaller bubbles generated the more dissolved organics removed.

Types of skimmers

Air Driven Skimmers

The earliest skimmers available at the hobby level, and the first skimmer I used back in ’82, were air stone driven. That is, an air pump drove an airstone at the bottom of the skimmer. Though such skimmers work, just not very well, the air stones had to be replaced constantly, since they clogged quickly in the marine water.


Venturi & Needle Wheel

Next came the venturi valve skimmers, a quantum leap forward. They became available around ’85 or so. A venturi valve does a much better job of removing dissolved organics than the above, and there are still venturi valve skimmers available today. They are head and shoulders above earlier models. Venturi valves chop the air better, making smaller bubbles.

About the same time needle wheel skimmers appeared. What they do is chop the air into smaller bubbles using a spinning, multiple tine, wheel. Both types work quite well, and there are high end models of both kinds.


Bypass Systems

Later there appeared skimmers that were designed to create more dwell time of the bubbles so more dissolved organics can be removed. Those skimmers have double or triple bypass systems, meaning the bubbles and their load of dissolved organics must go through sequential tubes before reaching the top of the skimmer and depositing their load in the skimmer cup. Venturi and needle-wheel based skimmers are available in such bypass systems.

Since the bubbles have more time to collect dissolved organics in bypass systems, they are more efficient, and expensive, than the above.


Downdraft Skimmers

Downdraft skimmers started appearing in the late 90’s. They are what most public aquariums use on their marine exhibits.

What they do is inject the water at high speed into the unit where air is added from valve of some type. Better models create such miniscule bubbles they look like foam. The water and air then goes down into the unit, then up into a separate chamber. As usual the bubbles rise and the skimmate is produced.

The upshot is that down draft skimmers process a massive amount of tank water very quickly, stripping it of dissolved organics. The Becket design is the type to look for if you’re shopping for a skimmer. This is the type of skimmer I recommend. There are several brands of them, all of them with their own patented valves.


Recirculating Skimmers

Recirculating skimmers are becoming more popular. They work by pumping water into the unit, where it is mixed with air by a valve, into a closed loop before it enters the main chamber for deposit into the cup. The thought is that the additional dwell time means more dissolved organics removed. However, I can’t see any advantage over a Becket Downdraft.


Another great benefit of protein skimmers is because by their very function, they produce a lot of dissolved Oxygen, which helps keep it at the optimal 8 mg/l, to the benefit of all the life in your tank.

There are several patented methods of mixing air and water sufficiently to produce the bubbles. One, spray induction, is the type of skimmer I use. Research thoroughly the skimmer you are interested in, since interior construction varies among brands. For example, there are low end venturi skimmers, and higher end, read more expensive, top quality ones.

Protein skimmers are one piece of equipment that you can’t cut corners on. Buy the very highest quality skimmer you can. Some come with a pump, some do not, the latter means you have to purchase one of those, too. Scale a skimmer rated for at least twice your aquarium size. Multiples skimmers may be necessary, depending on stand height. Properly used and maintained, a skimmer can be used for many, many years.


4 thoughts on “Protein Skimmers”

  1. Sandy

    I am re establishing a coral tank that had been ignored for a year. At first the simmer was filling up daily . Now I have added a damsel and the protein skimmer is not producing like it was . The coral seems to have mostly died but some still barely haging on. My tank is 55 gal. Am I overreacting? Makes some sense 1 fish doesn’t poop that much plus eats most of the yucky’s.

    One other question about my hydrometer…. If the salt is low do I add ? Some days it’s perfect mostly low.


    1. Cliff

      Is your skimmer new ? That would explain what is happening to it. New skimmers can take as long as a week of continuous use to break and start working properly. After the break in period, you typically have to make a few adjustments to the air and water flow before the skimmer will start working properly. Try adjusting it according to the manufactures instructions to start getting more skimate in the cup. With a low bio-load, the skimmer cup should still fill up in about a week, but the skimate may be a very light color. Even older / broken in skimmers can need adjustments from time to time to compensate for wear-n-tear on the pump.

      If you are taking about using a swing-arm hydrometer, then I would very strongly recommend getting a good quality refactormeter. The swing arm hydrometers are know to be off as much as 0.003. That could be what you are seeing but in reality have a very stable salinity level. It could also explain why your corals are dieing off. I would test your water with a refactormeter first before you start to adjust your salinity levels. Once you have done that, then you can adjust your salinity level by either taking a little tank water out and replacing it with fresh water (to lower your salinity) or taking out some tank water to mix a little more salt into it then return it to your tank (to raise your salinity). Just keep in mind you really should slowly make adjustments to your salinity as this will effect your other water parameters such as your pH.


  2. Howie Moore

    I am Howie Moore and I will like to know if you have Skimmer Unit.if yes,then get back to me with the prices for and the major credit cards you accept.Thank You.

    Best Regards.
    Howie M.


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