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Foam Fractionators - Protein Skimmers
Yet another most controversial piece of equipment, although its use has greatly increased in the last few years, thanks to several articles on the subject in Hobby magazines. My own position is very clear : they are necessary, they are here to stay, they must be carefully sized, and you may have to use ozone with them if your tank carries a high load of animal life, and many tanks usually do.
Protein Skimmers, or skimmers, as they are commonly called, are as important a component of a Reef Systems as the trickle filter itself. They are not, technically speaking, "filters", but let's not get too much into semantics.
Skimmers are mainly used to remove organic matter and free floating algae from the water, before they have a chance to break down, reduce the dissolved oxygen levels, and stress the biological filter in the process. Skimmers also remove some ortho-phosphates.
Proteinaceous matter resulting from excess food, undigested food, animal excretions, algae die-off, small life forms die-offs, etc... starts to break down in the tank water. Bacteria that are part of this process require oxygen and get it from the water, making less of it available to the other animals, including the bacteria in the trickle filter who need a lot of it themselves. This, in itself, is a first stress factor on all the tank's lifeforms, and on the filters (especially the biological filter).
The second stress factor results from the intermediate breakdown compounds produced during decay and mineralization. Many of these can be noxious, or stressful, at best. Some of these include : indoles, phenol, scatoles, organic acids, amines, nitrosamines, amides, etc. Preventing this protein matter from breaking down to begin with, prevents the formation of these intermediate compounds as well. The net result is less pollutants, less stress, and higher dissolved oxygen levels.
Naturally, even the best foam fractionators will not remove all proteinaceous matter from the water, neither will they remove all free floating microscopic and other algae. But they will remove a great deal of them. The best proof of their efficacy, the one I always like to point to, is the composition, and appearance, of the liquid-paste-like matter that collects in the skimmer cup. Just take a good look at it sometime. If you had not had a good and efficient skimmer, all of that material would still have been in the water, either as decomposed, or decomposing matter, producing numerous by-products in the process (and stress).
Since it is clear that skimmers are an efficient way of removing undesirable matter from the water, the only question that remains is how to size the skimmer correctly. Often, you are at the mercy of the manufacturer, and his recommendations, as to what unit is intended for your aquarium. These recommendations are often erroneous. At least that is what I have found, when trying different size skimmers on the same tank, to determine which model, size-wise, gave the best results.
Since the recommendations I referred to seem to be erroneous, where do they come from, and why are they given? I can only assume that they were arrived at by research at a time when Hobbyists kept mostly "fish-only" tanks, and that the recommendation only apply to such type aquariums. That would make sense, as it is unlikely that a manufacturer would knowingly give out wrong information.
Since the type of tank we are interested in is totally different from a load, maintenance and filtration standpoint, I would like to suggest that you disregard those recommendations, and look at the following table that was painstakingly arrived at over many many experiments, and then after you have done that, make your own judgment:
Factors influencing columnar skimming :
diameter of tube or chamber.
length of tube or chamber.
type of airstone used (bubble size)
amount of air blown into chamber
Factors influencing size of skimmer :
size of aquarium.
load of aquarium.
feeding habits.
maintenance and husbandry techniques.
sophistication of filtration.
Of the 9 factors listed, some are beneficial and some are not. For example, using the right kind of airstone is a positive step, over-feeding is a negative one. Some factors are influenced by others, e.g. the sophistication of the filtration depends not only on having the right filter, but also the right pump, blowing air into the biological chamber, having fine filters in-line, etc.
It becomes quite complex, therefore, to decide on what type of skimmer to buy. Our recommendation is : when in doubt between two models, choose the larger one of the two.
We suggest that you decide between 5 "general" models :
In the list that follows, circle the number of the situations that best applies to you, then add up all the numbers, or substract where minus figures are listed, if the situation applies to you. Once you have your total, refer to the recommendations at the end of this section as to which skimmer you should get. This is a fairly easy list to go through. If you do not want to write in the book, keep score on a separate sheet of paper.
Checklist for Sizing a Protein skimmer (for tanks up to 125 gallons) :
DEDUCT- You have a trickle filter that meets the requirements outlined in this book (deduct 6) -6 - You have a trickle filter that partially meets the requirements outlined in this book 3 - You are blowing a lot of air into the biological chamber -1 - The air pump you are using is small, old and you have not recently changed the diaphragm 2 - Your are not blowing any air at all in the biological filter chamber 4 - You have no trickle filter 20 - You have a trickle filter with DLS (<6 months old) 4 - Your trickle filter contains DLS and is at least 6 months old 8 - Add 3 points to your score per 10 gallons of water in your system. Not including water in the sump..... 3 - Tank has a low biological load ( be honest) 2 - Tank has a medium load 4 - Tank has a high load 8 - Tank has a very high load 15 - You are not using molecular absorption filters (6 discs or one pad per 25-30 gallons) 5 - You are using too few molecular absorption filters less than one per 25-30 gallons of water, but more than 1 per 50 2 - You are using about 6 M.A. discs, or one pad, per 25-30 gallons -2 - You are not using activated carbon 2 - You clean your mechanical filters more than once a week -4 - You clean your mechanical filters at least once a week -1 - You clean your mechanical filters about once every 2 weeks 5 - You clean your mechanical filters very infrequently 10 - You are not planning on using ozone 10 - You feed more than once a day 6 - You feed about 4 times a week 2 - You do not remove dead algae 4 - You use a Nitrate reducing compound -6 - You do not use such a compound 4 - You are using a cartridge type mechanical filter, and change it each time required -3
1989 A.J. Thiel. This checklist may be reproduced only if the name of this book, and the address of Aardvark Press is mentioned.
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