What do I test for in my Reef Aquarium?

The excitement and pleasure of watching an aquarium full of corals grow and develop is what continues to motivate us to be involved with our captive environments.  Not only for the vibrancy of the colors, but the feeling of accomplishment at observing and nurturing animals that just 10 15 years ago were considered impossible to keep alive.  Every year more and more people are enjoying success with fewer and fewer headaches.  Unfortunately though, many aquarists have ongoing issues with an imbalance in their artificial ecosystem that prevents them from having a perpetual satisfaction.  However, most of these issues can be easily solved with an awareness and understanding of a few integral points conducive to long-term success.  The following points are to empower new and seasoned aquarists alike with the knowledge needed to enjoy a higher degree of achievement.

Calcium

One of the major processes involved with coral growth and consequently healthy reef development is calcification.  Calcification is the process by which the animals and plants of the reef extract calcium from the surrounding water and incorporate it into their body mass for a net increase in size.  Calcium is considered a macro element. It is abundantly available and extensively used by most, if not all, of the organisms on the reef.   It occurs in Natural Seawater (NSW) at a level of 400 450 ppm consistently from reef to reef.  It is only exceeded in content by sodium, chloride, borate, and magnesium.  Oddly though, none of these other 4 is used nearly as much as calcium.  This is why so many aquarists talk about and regularly test for the calcium content of their tanks.  And, not by accident, aquarists who are vigilant about maintaining the calcium level in their tank see a consistent vitality in not only the corals they keep, but also the desirable coralline algae.

To maintain a proper calcium level, it is imperative to test for it at least once a week.  Just as not enough calcium can be detrimental, so can too much.  A narrow window exists relative to calcium content and healthy calcification rates.  Use a high quality test kit that has small increments of measurement, and maintain a level that mimics natural seawater

Alkalinity

Alkalinity is the content of carbonates and bicarbonates of water.  Alkalinity is responsible for the hardness of water, as well as a determining factor of not only the pH but also the stability of pH.  It is used as extensively as calcium in the process of calcification by corals and algae alike.  It is also consumed by the acids produced in the tank.  All the animals in our captive ecosystems produce acids as waste, which have an affinity by the nature of their molecular charge to bind to the alkaline molecules.  This is a natural process and is why the alkalinity contributes to the stability of the pH of the water.

The optimum range for alkalinity is between 2.8 and 3.6 meq./l.  Many commercial buffers exist to supplement the alkalinity content.  As a side note, most tanks will experience a pH shift within a 24-hour period.  This is mostly due to the fact that it is a closed system with a finite chemical content.  Photosynthesis and respiration are two important governing factors as to the extent of the pH shift.  The alkalinity of the tank is what determines how extensive the pH shift is.  Low alkalinity coupled with intense lighting or a heavy stocking load will promote a wide pH fluctuation.  This is why it is more important to track your alkalinity and use this figure to determine the need for buffer, as opposed to testing the pH and adding buffer.

In reef aquariums, a relationship exists between the alkalinity and the calcium content.  The relationship operates in the same manner as a seesaw.  When one is excessively high, the other will be excessively low.  If this scenario develops, then the water has an ionic imbalance.  This ionic balance can be expressed as a cessation of calcification, or the precipitation of calcium and carbonates from solution.  This is another potential problem that can be the result of adding excessive buffer based on a perceived low pH number.

PHOSPHATE

Phosphate is largely a by-product of feeding the animals in our tanks.  It exists in different forms and depending on the form is either a direct nutrient for nuisance algae or a reserve waiting for free space to fuel nuisance algae growth.  Another negative consequence of elevated levels of phosphate, is its ability to interfere with calcification.  The molecular charge of phosphate, and the molecular charge of calcium, gives them an affinity for each other.  This binds the calcium to the phosphate and renders it unavailable to the coralline algae and corals that require calcium for proper growth.  An appropriate level of phosphate is .03 ppm or lower.  Methods for lowering excessive phosphate are through water changes with phosphate free water, extensive algae growth, dripping kalkwasser, installing a protein skimmer or by using phosphate-binding medias.  Most hobbyists use multiple approaches to assure low levels of phosphate.

NITRATE

Nitrate is the end product of nitrification.  Nitrification is the process by which different bacteria consume ammonia (NH4), producing nitrite (NO2) and eventually nitrate (NO3).  Ammonia and nitrite are poisonous forms of nitrogen.  Nitrate is a relatively non-toxic form of nitrogen.  But, nitrate is a primary nutrient for algae.  Excessive levels of nitrate make it difficult to keep nuisance algae under control.  It also reduces the vitality and longevity of fish, invertebrates and corals.  Appropriate levels of nitrate are 10ppm or lower.  Ways to reduce nitrate are through water changes, limiting the number of fish (lowering the food input), extensive algae growth, installing a protein skimmer or denitrification.

Denitrification is the process by which bacteria consume the nitrate molecule under anaerobic conditions and produce free nitrogen gas as an end product.  Hobbyists with a mature deep sand bed (3-4) can witness denitrification.  Little bubbles will periodically rise from the sand bed.  This is free nitrogen gas (N2) produced by the bacteria deep in the sand bed.  Denitrification does not happen as quickly as nitrification.  There are more steps involved, and thus is only a major nitrate reducing avenue if the food input is limited

Conclusion

These are just a few parameters that are integral to long term growth and survival of fish and invertebrates.  They are explained in very basic format.  If you have questions on top of what is explained herein, come on in and consult with an AquaTouch employee.  We at are committed to providing the latest information, and highest quality products to make your reef keeping journey a rewarding experience.

Prepared by Scott Davidson