Activated Carbon

Typical appearance of activate carbon granules.

Introduction

Activated carbon is used to remove dissolved organic compounds, most typically exhibited by the yellow tint often seen in aquarium water. The tint comes from organic pigments which are products of bacterial decomposition of organic matter within the system.

Activated carbon can also be used to remove heavy metals from the water, such as copper and iron, and acts as a second stage (first stage is particle filter) for reverse osmosis and deionisation filtration of tap water (to remove chlorine/chloramine).

Usage

It is important that water is actually forced to flow through the activated carbon media. Simply placing a bag in the side of the sump will work to some degree, but poorly. Typical ways of using it include:

• canister filter
• chemical media column
• chemical media bag in sump or where outlet of protein skimmer flow onto it (good for removing ozone if used in the skimmer)

The media only stays active and of any real use for a couple of weeks, at the most. By that time, it will be covered in a biofilm, so absorption is greatly reduced, if not essentially halted. The film can be removed by vigorous washing with water or quick soak in acid. This treatment will allow another week or so of use.

Phosphate

Part of the activated carbon manufacturing process requires activation by contact with phosphoric acid. Therefore, some lower grades of activate carbons can add phosphate to the aquarium water passing through it, due to poor washing of the product after this phosphoric acid treatment step.

Regeneration

Regeneration is not possible for the average hobbyist, it requires high pressure, high temperature and washing by a strong acid (phosphoric acid).

Can get a little more usage by vigorous washing with water, or soaking in an acid (such as hydrochloric acid). This process will remove the surface biofilm (made up mostly by bacteria), improving access to the underlying activated carbon. But this typically isn't really worth the effort.

Gallery

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  Typically appearance and grain size. Scale is in centimetres, with smallest mark being 1/2 millimetre.

Resources

• An Overview of Activated Carbon in the Marine Tank by James Layton
• Granular Activated Carbon In The Reef Tank: Fact, Folklore And Its Effectiveness In Removing Gelbstoff — Part One by Richard Harker - Aquarium Frontiers Online
• Granular Activated Carbon In The Reef Tank: Fact, Folklore And Its Effectiveness In Removing Gelbstoff — Part Two by Richard Harker - Aquarium Frontiers Online
• Granular Activated Carbon, Part 1: Modeling of Operational Parameters for Dissolved Organic Carbon Removal from Marine Aquaria by Ken Feldman, Lauren Vernese, Karl Mueller and Kelly Maers - Advanced Aquarist's Online Magazine
• Granular Activated Carbon, Part 2: Modeling of Operational Parameters for Dissolved Organic Carbon Removal from Marine Aquaria by Ken Feldman, Lauren Vernese, Karl Mueller and Kelly Maers - Advanced Aquarist's Online Magazine
• Bacterial Counts in Reef Aquarium Water: Baseline Values and Modulation by Carbon Dosing, Protein Skimming, and Granular Activated Carbon Filtration by Ken Feldman, Allison Place, Sanjay Joshi and Gary White - Advanced Aquarist's Online Magazine
• Activated Carbon: HLLE Smoking Gun Found by Jay Hemdal - Coral