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.
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 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 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.