If you have an effective protein skimmer you won't need another one, and that's why many aquarists don't much care what's new. But for those who have a need for one, the considerations and options can be numbing. What size do I want? Should it be air driven or venturi driven? What will it cost, and what will the pump to operate it cost? How much room does it take, and as it attractive or ugly? What do I do with the slop and how often do I need to service the unit?
There is no best skimmer and no single answer. What is touted as the best skimmer one year is obsolete the next. Problems exist with all skimmers. Air-driven units require frequent replacement of the limewood air blocks and a powerful air pump (and frequent replacement of the diaphragm) in order to operate the unit deeply. Deep water is necessary for increased contact time between bubbles and water, but the greater water pressure must be overcome.
Counter-current venturi skimmers don't have these problems, but often require a big water pump (at a hundred bucks a pop). Downdraft skimmers often require big pumps, but are also tall in order to increase contact time. And how big should the unit be?
In fact, the size of the unit depends on the biological load (how much food you are putting into the tank each day that must be metabolized, and waste removed). Suffice it to say that most fish and other creatures are about 70 percent efficient, so 30 percent of all the organic material you put in must be removed from the water the next day by evolution of gas from the water surface or by removal as gunk in a skimmer or as plant/algae/microbial growth.
A skimmer needs to mix tank water with air. The more violent the mixing, the smaller the bubbles. The longer the contact time between water and air bubbles, the more gunk removed. The traditional means of achieving high contact time are height of the mixing column, increased number of bubbles and reduction in size of the bubbles (which helps keep them from rising out of the mixing column).
The AquaC is not a new idea but a scaled down version of some of the giant commercial skimmers used by public aquariums. Instead of a single venturi port (putting all its eggs into one basket), the AquaC makes use of jets of water shooting into the mixing chamber. These jets create bubbles, but the engineering of the unit optimizes their number and size. The result is a small volume mixing chamber crammed with fine bubbles just bursting to break free.
So far, you might ask, what's the functional difference between this and a good, quality venturi skimmer? One principle difference is the enormous mass of foam produced, but even more important is the powering of this skimmer with a relatively inexpensive powerhead.
Jason Kim sent me the mid-range Model EV-100 to test in my fish room and I gave it a thorough workout. Each of the three models has a particular powering pump recommended (see Table 1), and failure to use the correctly balanced pump will result in inefficient skimmer operation. A precision instrument, you need to use it according to factory specifications or you will not get optimal results.
I said it takes an inexpensive powerhead. Well, the Rio 2500 is not cheap, but it's powerful and a fraction of the cost of a water pump. It's also easily taken apart and cleaned, with replaceable parts when needed. And it takes little electrical power. At a flow rate of 300 gallons per hour (gph), it's not the most powerful around, but when running this skimmer it does yeoman duty.
The height of the water inside the unit determines the height of the early forming foam, so adjusting the mixing section water height is important. Following recommendations, I set up the EV-100 in the sump for my rack of 16 29-gallon marine tanks. I placed the skimmer on a platform (an overturned plastic tank) with the sump to attain adequate elevation A large plastic handle (like an outdoor water spigot handle) makes adjustment of inside water height by blocking the outflow port's diameter easy. As you close the port, the water and foam back up inside the skimmer and may rise through the overflow.
When I was able to get the unit adjusted just right, the water exited from the outlet (instead of from the overflow) and the foam rose where I wanted it to -- to the base of the collection cup. As the dense waste increased, it reached the outlet drainage port and slowly emptied. I connected a plastic tube to this port so the waste from the collection cup drains into a gallon jar.
During the first week 1 had trouble getting a dark, thick waste product, and it was putting out a lot of greenish yellow thin waste (and tank water). That's not bad, as it accomplished more frequent water changes (when you dump out a gallon of waste product you can replace it with newly made-up seawater).
But I'm a product of what I read (like you) and have been conditioned to want thick, dark waste. I eventually got the skimmer adjusted to produce what looks like old motor oil, and now I'm happy.
I compared the Aqua C's waste product with a hang-on skimmer of another brand that uses a similar powerhead, and found the Aqua C more effective. Granted, credit must go to the Rio 2500 (used by both skimmers) and to the correct elevation of the skimmer in relation to the discharge water level (automatic on the hang-on). But I like a product that delivers on its promises, that is built of high-quality components, including heavy impact-resistant plastic, is easy to use and comes with first-rate clear and detailed instructions for setup and maintenance.
The AquaC delivers on all points. The thorough, well-illustrated guide recommends weekly or biweekly cleaning of the collection cup to optimize waste removal, and I confess that I didn't do this. Even with my sloppy housekeeping I got excellent waste removal.
The only difficulty was adjusting the water level height below the foam. The dark plastic lower mixing box interferes with sighting from the side (unless I was willing to get down on floor of my fish room - but neither would you). From the top it's impossible to see the water level through the foam.
I dealt with this by cranking and adjusting the water level by trial and error. I'd recommend that future models use a clear or lightly tinted plastic box instead of this dark gray (almost black) box that interferes with viewing.
This is an excellent skimmer for tanks with a heavy bioload. It takes up little room and can be used outside a sump, or outside the tank. Instructions and illustrations are provided for all configurations.
Most people with reef tanks will do fine with the smaller model EV-60 or the EV-100 for reef tanks over 100 gallons. I'm a firm believer in all the skimming power I can get, so I'll leave the selection up to you. Note that the largest model (EV-180) uses the same powerhead but has a larger mixing chamber, enabling a greater flow through. It would be a good bet for pet stores or reef tanks over 300 gallons.
© Aquarium Fish Magazine/Robert J. Goldstein, Ph.D.