Activated carbon gets the water so clear that fish seem suspended in space! This was one of my early statements on this fantastic filtering medium, and decades later I am even more enthusiastic about the fabulous filtering qualities of activated carbon. In my opinion it is without equal in the aquarium field, and to do without it is to do without a sparkling clean aquarium where the water becomes invisible and the living jewels of the sea sparkle in water that is not only scrupulously clear but chemically and biologically clean. What more could be asked of a filtering medium?
Yet activated carbon is not well understood in the aquarium field - particularly in the salt water world. Improperly used, it can wipe out a tank of expensive fish overnight. Properly used, it can keep a tank full of fish in healthy condition for years without a single change of water. In fact, with the advent of the all glass tanks, a good undergravel filter with silica sand and a good outside filter that reaches all the way to the bottom with the siphon stem, it appears possible that a salt water aquarium could remain healthy and in good condition for a period of ten years without a single water change, provided, of course, activated carbon is used properly in the filter and good aquarium maintenance is observed at all times. Therein lies the solution to the successful use of activated carbon in the aquarium. You must know what you are doing! Otherwise you will have little or no success with the carbon.
Success with activated carbon depends upon several factors chiefly of which is the carbon itself. Like everything else, there is a great difference in carbons. Some are very cheap, others costly. Some are made of animal bones, wood, and various other materials. We use a product made from coconut shell, which we feel is consistently more pure and chemically inert than other products. It may or may not be the best, but I personally have tested it over many years in well over a thousand salt water aquariums under all types of conditions. It does the job and does it well, which is good enough for me. Until I find a product that works better, I am well satisfied with it. I have tried other brands of carbon of course. Some worked good; others were lethal.
Activated carbon is a powerful filtering agent. They used it in cigarettes, space ships, and deep sea submarines. It removes practically everything from the air, and in our instance, from the water. Because of its ability to extract gases, odours, fumes, etc., from the air, it can pick up poisonous substances from the air simply by being stored near them. In the case of chemical houses or pet stores, an opened case of carbon can absorb lethal doses of insecticides, paints, and dangerous chemicals, which could eventually cause problems in the aquarium. This sometimes causes unexplained failures with carbon when used in the aquarium. It also points out that activated carbon should be handled and stored with great care in air tight bags, especially if it is stored in a room with highly volatile substances. Otherwise it will be contaminated and unfit for use.
As pointed out above, there are many grades of carbon. Choose a known brand and one that is used by your local dealer if he is using it, or order a good quality carbon. The better grades of carbon will vary in price per pound, depending upon whether it is cured or fresh. At the higher price it seems expensive, but it will last a long while. Contrary to popular opinion, carbon does not lose its efficiency after a few hours in the aquarium. Quite to the contrary, it improves vastly with age! Well aged carbon is completely safe to use, for it is neutralised by its constant use. It can be used over and over again, even for years if it is not contaminated with oils or dangerous chemicals. Those who would state that carbon is not an effective filtering medium should try it sometime. I don't know where they obtained their information, but it's a fact that carbon five years old will turn a dull, dingy, brown colored aquarium into a thing of sparkling clean water as clear as distilled gin. Well, perhaps it's not the carbon that gets the water clean when you place it in the filter. It must be the spirit from the great beyond! Or perhaps these people don't know what they are talking about. I'm inclined to believe the latter.
The safest way to use activated carbon is to cure it in salt water for a few weeks before placing it in the filter. Then rinse it well in fresh water. It is best to start it in the filter when the tank is first set up and the fish have not yet been added. Let the filter operate for a week or two with the water, and then add the fish, floating them in a container and introducing them gradually to the aquarium. Carbon filtered water is different from unfiltered water. Salt water fish cannot take ANY sudden change from one type of water to another. The same is true when they are being introduced to a carbon filtered tank or when their aquarium is to have carbon added to it for the first time. It must be done very gradually so that the fish can slowly become adjusted to it. If a tank has been set up for several months, the sudden use of carbon can prove disastrous. In this case, a small amount of carbon, say a teaspoonful to a tablespoonful, should be added to the empty filter once or twice a week, gradually building up the carbon until the filter is full. But the carbon should be aged before use. This is most important.
Many people write inquiring whether or not glass wool or nylon, should be used in conjunction with the carbon. This is a matter of choice. If you have a good filter, you can use just the carbon, but if the filter has wide slots in the bottom, a little nylon or orlon will keep the carbon from passing through the slots. We don't recommend glass wool, as the synthetic floss is safer to use in the aquarium and easier to handle besides. A little of it placed above the carbon will help trap additional dirt and is easily removed when dirty, which will help keep the carbon clean longer.
We also get many inquires about resins for keeping the water clean. To date, we have not seen any resins that would keep the aquarium water clean, and we have tried some of them. The only time we recommend them is when aquarium water needs softening, in which case they probably do help.
We have used the activated carbon all by itself with nothing added to it for most of our experiments, and the results have been phenomenal to say the least. It will get the water unbelievably clear arid keep the fish in perfect condition. We have even reclaimed chemically coloured water almost the colour of coffee, which was discoloured by adding copper sulphate and sulfathiazole sodium to the same tank for disease control. We had to change the carbon a couple of times, but it did the job. It got the water so clear you couldn’t see it, and the water was perfectly healthy even though it was nearly two years old! We put in a large variety of both Atlantic and Pacific fish and they flourished in the peak of health and splendour.
Activated carbon can't do everything. It can't cure a sick fish. It can't keep an aquarium clean if you aren't using enough of it or if you overfeed or put some bad coral in the tank. Everything has its limitations. But if you use it correctly, a half pound to a pound for ten gallons depending upon other filtration, number of specimens, etc., and use it in a good filter so it can do its job proper]y, it will give you the cleanest water you have ever seen. You'll have to wash it when it gets dirty and dry it in the sun every now and then, but this is a small task and takes but a few minutes.
Use good carbon and use enough to do the job. Your reward will be the cleanest water you can imagine, as clear and sparkling as a mountain spring. The colours of your fish will be pure poetry