Organic carbon dosing has become a very popular reef aquarium practice in recent years. It’s a very effective and easy way to remove nitrates and phosphates that cause algae and can harm your aquarium’s inhabitants. What exactly is organic carbon dosing? Why should you dose with organic carbon? How does it actually work (scientifically), and how do you implement carbon dosing?

WHAT IS ORGANIC CARBON DOSING?
Organic carbon dosing is the process of adding a bioavailable source of carbon to your aquarium in order to increase the population of beneficial bacteria. The beneficial bacteria will naturally lower nutrient levels.

Organic carbon is not the same thing as the black filter carbon that is commonly used in aquarium filters. Organic carbon is usually a form of sugar or alcohol; Examples of organic carbon include Two Little Fishies NPX Bioplastics.

WHY YOU SHOULD DOSE ORGANIC CARBON?
In aquariums natural nitrifying bacteria break down fish waste from ammonia to nitrite and from nitrite to nitrate fairly easily. Most established aquariums have ammonia and nitrite levels that are consistently zero. However, nitrate tends to accumulate and can be toxic to the tank’s inhabitants. It also causes unwanted algae growth. Traditionally this nitrate is removed through water changes, but water changes are labor intensive and in some cases costly. Organic carbon dosing feeds denitrifying bacteria which converts nitrate to nitrogen gas. Nitrogen gas naturally dissipates into the surrounding air, removing it permanently from the aquarium.

HOW DOES IT ACTUALLY WORK?
Organic carbon dosing works when you have the ideal ratio of elements needed for bacteria to grow. The ideal ratio is 106 carbon to 16 nitrogen to 1 phosphorus. This is what is called the Redfield Ratio. The nitrogen in aquariums is in the form of nitrate, and the phosphorous in the aquarium is in the form of phosphate. Aquariums that do not have added organic carbon will run out of carbon before running out of the nitrogen (nitrate) and phosphorus (phosphate) that need to be eliminated. The bacteria growth is stunted due to the lack of organic carbon.

When the bacteria in an aquarium are provided sufficient organic carbon, through carbon dosing, the bacteria will multiply until they use up either all of the nitrogen or all of the phosphorus. Usually the bacteria use up the nitrogen and leave a little bit of phosphorus, which results in an aquarium with no detectable nitrate and minimal phosphate.

HOW DO YOU IMPLEMENT CARBON DOSING?
There are 2 common ways to dose with organic carbon: liquid carbon dosing and solid carbon dosing. Liquid carbon dosing involves adding a product such as Brightwell Aquatics Reef BioFuel. To dose with liquid carbon simply add a small amount of the liquid carbon to your aquarium on a daily basis. Follow the manufacturer’s recommendations and adjust the amount dosed based on the nitrate levels in your water. If you want to avoid the work associated with dosing the aquarium daily, you can use a dosing pump to automate the dosing process.

Solid carbon dosing uses biopellets (also called bioplastics). Biopellets are small sphere-shaped pellets that are made of organic carbon. Two Little Fishies NPX Bioplastics,and Reef Octopus BioSpheres are recommended. These pellets need to be placed in a specialized reactor. In the reactor the pellets are tumbled. Bacteria accumulate on the surface of the pellets, and the pellets break down nitrate. The tumbling constantly removes old dead bacteria from the surface of the pellets and then sends it back into the aquarium where corals can eat it.

When choosing a reactor for biopellets it is best to use a churning style reactor rather than an up flow reactor. Some good reactors are the Lifegard Aquatics Turbo Reactors and Reef Octopus OCTO Bio Churn Reactors. Biopellets do not need to be changed out as they naturally dissolve away as bacteria eat them. If you start with the manufacturer’s recommended amount of biopellets you will probably not need to refill the reactor chamber with more biopellets for about six months. No other maintenance is needed.