Juggling Nutrient Levels for an Optimal Reef Aquarium

Nutrients have always been a major source of debate and popular topic within the marine aquarium hobby. Questions regarding the amount, when, what kind and even if nutrients should be part of our aquariums at all have been debated and studied for years now. Trying to get the facts straight and decide what is right for you and your aquarium are pertinent to your livestock, macroalgae and nuisance algae that may or may not be present.

As is the case with many living animals in a marine environment, their is a dividing line between feeding too much and just right. What may be ideal for one particular species of coral enabling it to thrive may not be advantageous for another. A great example of this is Xenia, which is a species of soft coral. Xenia thrives under conditions where nutrient levels are higher than would be for standard reefs of the world. The addition of carbon and very limited dissolved organics and other nutrients normally causes reduced growth, On the contrary, a hermatypic coral such as Montipora Digitata favors limited nutrient water or even nutrient deprived water parameters as they receive most of the nutrients required by them in the form of light which their host zooxanthellae provides as a result of photosynthesis.

Trying to limit the amount of phosphates, silicates, nitrates and other forms of nitrogen will, often times, be the determining factor as to whether or not and how much algae growth you have in your tank. Diatoms, cyanobacteria, hair and bubble algae and other forms of microalgae can be determined by the amount of nutrients in your water. Depending on the amount of corals as well as the types of corals as well, you may or may not want to deplete nutrients from your water totally. Many filter feeding animals such as Tridacna Clams, fan worms, copopods, polychaete worms, amphipods, gorgonians and sponges rely on dissolved nutrients for their success. Many forms of corals also absorb and adsorb nutrients through their outer tissue layer for their growth and survival. Octocorals are mainly the ones that benefit from higher than normal nutrient levels.

If you plan on or are maintaining hermatypic corals such as Montipora, Acropora and many other small polyped stony corals, then you will want to have pristine, nutrient poor water. Limiting factors such as feeding amounts and how many times a day and fish bioload will help to reduce nutrient levels from elevating. Efficient and effective skimming and other forms of filtration, water changes, clean up crew hosts and housing macroalgae and sea grasses will also help to reduce nutrient levels and decrease microalgae and other unsightly conditions from imploding by feeding and competing for nutrients that would normally be consumed by nuisance algae.

Your best bet is to decide which side of the fence you would be best on based on the corals you possess and/or plan on purchasing in the future. I can say for myself that with a large assortment of filter feeders and octocorals, maintaining a higher than normal nutrient level in my tank such as a 10-ppm nitrate level, my tank is thriving. My Xenia, Discosoma mushrooms and Kenyon Tree corals are growing like weeds and with limited nuisance algae growth. With a fine balance of feeding, filtration and bioload of fish, invertebrates and corals in a closed system environment combined with the myriad of other aspects, essential in creating and maintaining a successful and thriving marine aquarium, you will not be disappointed.

Reefs are characteristic of two distinct biotopes. Those that are surrounded by nutrient poor waters such as fore-reef slopes and lagoons and those that have a surplus of nutrients such as upwelling reef areas and tidal zones. Coral reefs are a complex ecosystem comprised of both primary producers (ie. phytoplankton, zooplankton and algae) as well as consumers (ie. fish, invertebrates). Food and nutrients are vital to life, reproduction and growth of all living animals. Food provides energy and for the energy requirements to be met, total energy demand must be met. This may come in the form of heterotrophic modes of feeding or autotrophic modes. Corals that are not reliant on zooxanthellae and light for that matter are assumed to be heterotrophic and will need to be fed-target feeding being the best method for these corals to survive through ideal nutrition,

On the other side of the field are the corals that need to be fed, preferably though strong and intense light to help generate the surplus of nutrients required by zooxanthellae to expand further up line to the corals hosting zooxanthellae, are termed autotrophic. Being able to handle your divers population successfully by offering them what they need to satisfy the energy and nutritional needs of corals is when you will be able to sufficiently and accurately satisfy your livestock without polluting you water causing nuisance algae outbreaks and depreciate growth and reproduction rates.

You by no means want to deprive nor neglect the food requirements needed by the various livestock to live a healthy life, just to create that fine line that will award you and you livestock an enjoyable and thriving closed system environment.

The overall key to an awesome looking and enjoyable tank filled with a plethora of living animals can be obtained by finding the fine line between food input and export/assimilation to ensure the dissolved nutrient level remains low enough to support all forms of live.

Starving your tank is the wrong answer in creating a nutrient poor aquarium, if that is what your ultimate goal is to be. Instead, by providing ample amounts of live sand and rock as well as water changes and efficient mechanical filtration, combined with the filter feeders, detritivores and various bacteria to handle the aerobic, anaerobic and anoxic areas of the benthic zone of your tank. Proper testing will also help you to closely monitor nitrates, phosphates, silicates and other common nutrient components before they become a major disaster.