Organics Compounds In Reef Aquarium
What are Organic Compounds
An organic compound is any member of a large class of chemical compounds whose molecules contain carbon and hydrogen atoms. There is actually no official definition of an organic compound. While some text books define an organic compound as one containing a carbon and Hydrogen bond, other state that if a molecule contains carbon it is organic.1 To this naming convention, Carbonic acid and bicarbonate ion are the two primary exceptions that aquarists encounter.2 Natural waters, freshwater aquariums and saltwater aquariums contain a great variety of soluble organic compounds. We often classify them as being either dissolved organic matter aka DOM (can pass through 0.2 – 1.0 mm filters) or particulate organic matter aka POM (won’t pass through 0.2 – 1.0 mm filters).2
Negative effects in saltwater aquarium:
1. Those organic compounds can stimulate the growth of heterotropic bacteria thus increasing demand for oxygen in the aquarium, producing carbon dioxide, lower pH, and lowering redox potential which promote algae such as hair algae and cyanobacteria despite low nutrient levels.4
2. Some foaming in the sump or in the corners of the tank,3
3. An oily film or cloudy layer on the water surface3, and
4. Organic Compounds can tint aquarium water to a yellow color. This decrease the intensity of light reaching photosynthetic organism.2
5. High levels of organics can also tax a protein skimmer to the point where nitrates and phosphate removal becomes minimal.3
6. There is now firm evidence that organics stunt fish growth. In addition, at moderate organic levels, corals and invertebrates tend to close or cease reproduction.3
7. Odor. With the exception of rotten egg odor that is mostly generated in anaerobic environments, any smell is an organic molecule.2
Positive effects in saltwater aquarium:
1. As stated previously, organic compounds can benefit growth of some organisms. This is also the case for some of the organisms we want to thrive (like corals). Unfortunately, relatively little information is available about what these organic materials are doing.2
2. Dissolved organic material may bind to and modulate the solubility, bioavailability, and toxicity of many metals, such as iron and copper. This could also be a negative effect depending on the metals.2
How to control excess dissolved organics?
There are many ways to control the amount of organics in your aquarium. Remember, there are two general types of organic material: dissolved organic matter aka DOM (can pass through 0.2 – 1.0 mm filters) and particulate organic matter aka POM (can’t pass through 0.2 – 1.0 mm filters).
1. Water changes with DO/DI water.
2. Cleaning the mechanical filter media of your filtration systems often. You should also clean the substrate and live rock. This is where the majority of the particulate organic matter will get trapped.
3. Activated carbon removes organic compounds by adsorption.
4. A protein skimmer removes dissolved organic matter.
5. Any other ideas?
Conclusion
Organics can be positive or negative for the reef aquarium. Unfortunately, it is difficult to determine exactly which organic compounds are present in the aquarium and what specific effects they might have on different organisms. What I think is important to remember is that organic levels should be control to avoid high levels that could have negative impacts on the overall health of the reef aquarium.
References:
1. Organic compound, Wikipedia.
2. Organic Compounds in the Reef Aquarium, Reefkeeping Magazine™.
3. Does a Reef Tank Need Carbon? by Joe Jaworski.
4. An Overview of Activated Carbon in the Marine Tank By James R. Layton
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