Introduction

I receive many phone calls and email messages enquiring as to whether:

• activated carbon is really necessary,
• if it is, which type is best,
• how much activated carbon to use per gallon, or some other measurement,
• how to change it without stressing the system,
• and how often activated carbon should be changed,
• how one can tell when it should be changed (is there a test),
• should anything be done to it before using it,
• what differentiates a good one from a not so good one,
• what is the true story on leaching of phosphates
• and so on ...

Activated carbon, in its many forms, has been used for decades now in both fresh and saltwater aquariums. It's appeal appears to be greater in saltwater and reef aquariums because of the perceived larger amount of pollution that is generated in such aquariums.

Granted this may very well be so, although no one has ever proven it (my own opinion is that different types of chemical processes occur rather than more pollution creation), but if this is indeed the case, then the protein skimmers we use should remove a great deal of this additional undesirable matter, as most hobbyists know. Of course, to make this process succeed, skimmer efficiency comes into play a great deal (what type is used, is it large enough, can it handle the bioload, it is running optimally, is the hobbyists adjusting it when necessary, is it reliable, etc).

Some of the forms activated carbon comes in and is sold as are:

• G.A.C. or granular
• Pellets of various thickness and length
• Rods of various length
• Spheres or balls of various size
• Powder (size of powder particles may vary)
• Impregnated pads
• Mixed with resins
• Mixed with other compounds such as phosphate and silicate removers
• and so on. I am sure I overlooked a few.

Are there really reasons to use GAC

Given the uncertainty about the amount of pollution generated in salt water and in reef aquariums, and the very widespread use of foam fractionators, is there a reason to use activated carbon in addition to what we are already doing (and that includes using live rock, live sand, efficient skimming, trickkle filters and other types and so on on - not all are used by every hobbyist of course)?

I think so.

Let me try to explain why:

• Whereas skimmers remove a great deal of pollution, they do not remove all undesirable compounds,
• Skimmers may not always be running at optimum levels,
• Skimmers used may be too small for the bioload,
• Certain breakdown components of organic material are removed by activated carbon more efficiently,
• certain pollutants are not removed by the skimmer but are by GAC or other forms of activated carbon,
• A small amount of activated carbon can make the task the foam fractionator has to perform a little easier and more efficient,
• pesticides, algaecides, etc. are removed by activated carbon and may not be removed by protein skimming. There is not definitive study on this but experience tends to support this.
• Airborne pollutants appear to be more susceptible to removal by good quality activated carbon than by protein skimming,
• Yellowing of the water is avoided by using activated carbon (see later for how the carbon should be used and how much of it is necesarry in my opinion (mine only).
• tar and nicotine - for those of us who are nicotine challenged (such as myself)- are removed by activated carbon. It is not clear whether protein skimming actually removes these and related compounds.

Observations about the use of GAC

As you can see there are many reasons and justifications for using carbon in addition to a protein skimmer. How much should be used and whether one should run carbon continuously are an often debated topic. I do not believe anyone has actually come up with a definitive answer (as is the case for so many areas of this hobby). All we can do as hobbyists is go by our personal experiences and what other input we get from hobbyists who do use activated carbon. At least we have some anecdotal evidence that using carbon has benefits although no scientific proof.

When enough anecdotal and positive evidence of benefits exists though, one (including myself) will have a tendency to take that evidence that carbon does indeed benefit the tank. This is a normal reaction and one that we rely on for many of the things we do to our aquariums.

Whenever enough hobbyists report good results with a certain technique or product, other hobbyists will start adopting that technique or will start to use that product too.

A good example of this would be the use and benefits of Vitamin C. I have been writing about it for years and years and have recommended it and still do for many a problem. As the experiences of hobbyists who had positive results were more widely reported, yet more hobbyists started ordering our Vitamin C and then started to report similar positive results.

Even though at this stage there is no scientific explanation of the kinetics of Vitamin C in aquariums, the number of positive experiences is now so large that many hobbyists are finally convinced that C can be used beneficially as a water additive and not just as a food supplement.

The same applies to the use of activated carbon. No one can really prove that is it beneficial, but observing tanks on which it is used and tanks on which it is not, and then making comparisons, leads to the conclusion that using some amounts of carbon is indeed beneficial.

What has changed over time, especially in reef tanks, and to some extent in fish-only tanks, is the recommendations regarding quantity. Whereas a few years ago, more was better, it now appears that hobbyists are more cautious and use far less activated carbon than they did before. The main concern is depletion of beneficial nutrients and the possible onset of lateral line disease if too much carbon is used for too long.

Whereas no concensus exists on how much carbon should be used, what appears to be the trend nowadays is a shift from using a large amount continuously, to using smaller amounts and using them intermittently not continuously. That is what I personally now do and recommend.

How much GAC should one Use

The amount that I have found to be sufficient in

reefs is:
• about 3 level tablespoons per 50 gallons of actual water
• ran once a week, for approximately 12 hours
• I then remove the carbon, spread it out in a shallow tray and let it dry out
• one week later I use it again for 12 hours
• I change the carbon based on the carbon yellowing test results (see below)
• I also maintain a 5 ppm Vitamin C concentration in the tank at all times
• I add Vital Gold every day (based on product label recommendations)
• all other supplements needed for reefs are added as required

in fish-only aquariums:
• about 3 levels tablespoons per 50 gallons of actual water
• ran twice a week for 18 hours
• the same is the done as described above with regard to drying and changing the carbon
• Vitamin C is ran at 5 ppm and the necessary amount is added every day
• A complete supplement is added as per label instructions

Additional Useful Information

The type of carbon I use is pelletized vegetable base carbon, treated for use in salt water (also refered to as Cocunut shell).

I use the carbon yellowing test (TAT brand - which I believe is the only company that makes one). This is a piece of acrylic that has yellow marks on it. I immerse it in the tank and if I can see the yellow marks I know the carbon is still working fine. If I cannot see the yellow marks I know that the carbon needs to replaced. The reason for this is that this indicates an increase in yellowing matter (Gilvin) in the water, preventing me from seeing the yellow marks. When such an increase occurs, the activated carbon is no longer removing albumin and yellowing matter and is thus for all practical purposes, spent and needs to be be replaced.

This is the only way I know of testing the carbon that is simple and extremely fast. There are other methods but they are more elaborate and require more expensive tests. The carbon yellowing test is reusable over and over again and does not require more than a minute or so to perform. The test is very inexpensive as well.

Using large amounts of fresh carbon at once changes the water chemistry rapidly in my experience. Rapid depletion of oxygen can occur especially if the better brands are used. This can be overcome by pre-treating the carbon. Soak it in tepid water for about 20 or so minutes and then it should be ready to be added to your aquarium. Do not use large amounts though (see above).

Should you force the water through the carbon or should you just let it flow by and over the carbon? Various authors differ on this subject and no conclusive tests have demonstrated which one of the two is actually the beter method. Using caution by not overusing carbon is probably the better route to go until more is known about exactly happens in both instances. Pre-treating the carbon though, as described, should solve the rapid change in water chemistry.

Does carbon remove too many desirable elements? It certainly can and one should add a complete additive to the aquarium to counteract this. There are several on the market that are made for reefs and that have been improved over the years. Those are the ones that I would opt to use.

Phosphate Leaching

What is the truth on phosphate leachings? All carbon leaches "some" phosphate. That is its nature. All carbon removes iodine as well so using too much of it will deplete your iodine and will add some PO4 to the tank. The better brands of carbon though leach so little phosphate that once it is diluted in the aquarium the actual levels will be so low that they will be well within the ranges recommended (low PO4 level e.g. around 0.03 ppm). There are no carbons that do not leach any phosphates in the tank. The answer is to use a high quality brand that leaches very very little PO4. You can test what amount is given off by the brand you use by adding 1 tsp to a gallon of water, letting it sit for about 30/45 minutes and then testing for phosphate.

After you come up with a result, extrapolate and calculate how much that would represent as a concentration for your tank, and if that amount is real low (say 0.01 or 0.02 ppm) you have a carbon that is of excellent quality.

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