Introduction to Calcium & Alkalinity Maintenance

Introduction to Calcium & Alkalinity Maintenance

Michael Paletta - Guest Author

One aspect of keeping reef aquariums that is starting to gain significant attention is the need to supplement calcium and the easiest means to do so. Until the late 1980's, water changes and the dissolution of calcium substrate were thought to keep calcium levels high enough. Consequently, a calcium supplementation regimen was not deemed necessary and additional supplementation was not readily practiced.

We now know that virtually all corals, as well as coralline algae, require constant supplementation of calcium in order to thrive. As coral colonies and coralline algae grow and spread, the demand for calcium increases as they utilize and deplete more and more calcium. Calcium supplementation helps meet these biological demands by replenishing calcium levels in a closed reef system.

The concept of supplementing calcium in the reef aquarium was first described in the late 1980's, when the Berlin System for keeping corals was introduced to the public. This was a significant moment since little attention was paid to the coral's need for calcium for them to thrive and grow, prior to this series of articles.

Initially, the only method described was the use of calcium hydroxide (Kalkwasser) dissolved in water to replace water that had evaporated. As reef aquariums became more sophisticated and stony corals and clams became the dominant features in these systems, more sophisticated methods of maintaining calcium levels have developed.

The methods that are currently being employed include: Kalkwasser, Kalkwasser and carbon dioxide, Calcium chloride and buffer, balanced liquid or dry supplements, a calcium reactor or a combination of these methods.

No single method is utilized exclusively since each method has its own particular shortcomings and is not universal or practical in all reef systems. However, it is still relatively easy to maintain the proper calcium level in most reef aquariums (just above 400 ppm, the level of natural seawater) as long as these factors are understood and managed.

We'll discuss the advantages as well as the shortcomings of these methods in a series of articles so you can determine which method is best suited for your particular situation. Remember, calcium demands will vary from aquarium to aquarium and a single approach may not be adequate. Consider tinkering with these methods to tailor an optimal supplementation method for your system.

The Importance of Regular Calcium Testing

Much too often, many reef hobbyists quit testing calcium levels once a regimen for supplementing calcium has been established. However, calcium supplementation is not a static process. It is part of an ever-changing organic process where the demand for calcium increases as coral colonies (both soft and stony), coralline algae, and other marine invertebrates that actively utilize calcium begin to grow and spread. Larger amounts of calcium are required to sustain this healthy growth.

Do calcium levels increase as your aquarium ages?

Calcium requirements tend to increase in most reef aquariums as they grow and mature. As a result, your old supplementation regimen may no longer be adequate. If regular testing is not performed to monitor calcium levels, it is extremely easy to allow levels to drop precipitously. In reef aquariums heavily stocked with corals and invertebrates, it is crucial that calcium levels be assessed every two weeks; or even better, once a week. Alkalinity should also be measured and monitored since there is a relationship between calcium and alkalinity levels.

What is the relationship between calcium and alkalinity?

If calcium levels get too high (over 500 ppm), there is a tendency for alkalinity to drop, affecting the buffering capacity of your aquarium water. Without adequate buffering, pH levels become susceptible to fluctuations. Conversely, if alkalinity gets too high, calcium levels will tend to fall as calcium precipitates out of solution in the form of insoluble calcium carbonate, also causing pH fluctuations. Ideally, calcium levels should be between 400 and 450 ppm, while the alkalinity should be between 2.5-3.5 meq/L (7-10 dKH).

Several reliable testing kits are available to help measure and monitor calcium levels. There are also testing devices for measuring alkalinity.

How often should I check calcium levels?

It is important to monitor calcium and alkalinity levels weekly and supplement accordingly to keep them at proper levels. Low calcium levels negatively affect the growth, health, and coloration of corals. What little growth that may occur result in thin, spindly branches lacking vivid coloration.

Kalkwasser as a Method of Calcium & Alkalinity Supplementation

Kalkwasser - German for "limewater," it is a highly concentrated solution of calcium hydroxide in water with a high pH of 12.00+ used to supplement calcium and maintain high pH levels in reef aquariums. The popular use of calcium hydroxide or Kalkwasser became the method of choice in the United States for most of the last decade, surpassing calcium chloride and buffer as the preferred calcium supplementation method. Kalkwasser has been the method of choice for European aquarists for the past twenty years, clearly suggesting the effectiveness of this method.

Kalkwasser is simply calcium hydroxide dissolved in water so it is very straightforward to use. There are many different manufacturers of Kalkwasser including Kent,Seachem, and Warner Marine, all of them having relatively the same high quality.

Advantages

  • Readily available and relatively inexpensive.
  • Clean - Kalkwasser adds virtually nothing to the water that is deleterious, only calcium and hydroxide ions.
  • Reduces phosphate levels - Kalkwasser causes phosphate to precipitate out of solution as calcium phosphate making it biologically unavailable for algae.
  • Easy to prepare - Simply add the dry powder to water and shake. When the cloudy mixture settles, use the clear liquid as make-up water.
  • Minimizes pH fluctuations - Dramatic changes in pH cana be reduced when Kalkwasser is slowly added at night when pH typically drops in the aquarium.

Caveat

Despite its advantages, there are some shortcomings to the use of Kalkwasser.

  • Caustic - Kalkwasser is a caustic alkaline agent so care must be taken during preparation, making certain not to inhale the dust. Kalkwasser has a very high pH (12.00+) so it should not be introduced into the aquarium in large quantities or it will dramatically raise pH to excessive levels and cause the precipitation of Alkalinity.
  • Needs to be freshly prepared - Once prepared, the Kalkwasser solution should not sit for very long or it interacts with atmospheric carbon dioxide and converts into insoluble calcium carbonate. Kalkwasser solution should be prepared daily before it is added to the aquarium.

The use of Kalkwasser is a very good method of supplementing calcium for small to medium sized reef aquariums. For best results, Kalkwasser should be trickled in at night and a buffershould be added regularly. The dynamics of every reef aquarium changes over time so regular testing is necessary to monitor these changes.

Calcium Chloride (& Buffer) as a Method of Calcium & Alkalinity Supplementation

The use of Calcium chloride (for example, Kent Turbo Calcium or Warner Marine Calcium) was probably the first method of maintaining proper calcium levels employed by most seasoned reef hobbyists. Calcium chloride is widely available, inexpensive and it dissolves rapidly into solution. But when it was understood that calcium chloride could deplete the buffering capacity of an aquarium, (if added too quickly), its use was paired with buffering compounds, such as Seachem Reef Builder or Marine KH Buffer w/ Magnesium, to maintain proper alkalinity.

Advantages

  • Inexpensive and readily available.
  • Dissolves rapidly into solution.
  • Easy to use, precise dosage can be added since it is possible to mathematically determine how much is needed.

Ideal Application

The use of Calcium chloride is a simple and easy way to maintain calcium levels for small aquarium systems or ones that do not have high calcium demands. Aquariums with small amounts of coralline algae or small population of soft corals are examples of such aquariums. If you are maintaining this type of reef aquarium with relatively low calcium demand, this method should work without producing the problems described.

Regardless of the method, maintaining proper calcium levels go hand in hand with maintaining proper alkalinity levels as well as testing and monitoring these levels. When employing any calcium supplementation method, it is crucial to test for both calcium, alkalinity and pH levels in your reef system.

Caveat

  • Affects Alkalinity - When used alone, supplementation with Calcium chloride can deplete the buffering capacity of an aquarium. This can be corrected by adding buffers.
  • Improper use may result in "See-Saw" effect where calcium chloride and buffer need to be added regularly to counteract the effects of the other.
  • Certain elements may begin to accumulate to unnatural levels over time. In particular, sodium and bromide levels may build up since most buffers contain high concentrations of these elements. Remedied by performing more and larger water changes.

Balanced Supplements as a Method of Calcium & Alkalinity Supplementation

In order to overcome the problems described in the independent supplementation of calcium and alkalinity (e.g., Calcium chloride and buffers), several manufacturers have devised balanced formulas for maintaining both calcium and alkalinity. These include Tropic Marin BioCalcium, C-Balance, and Seachem Reef Advantage Calcium.

These compounds, available in dry or two-part liquid formulations, are capable of maintaining both high calcium levels and alkalinity without causing a build-up of unwanted compounds. This method of maintaining calcium and alkalinity in reef aquariums has become very popular due to their ease of use.

Advantages

  • Readily available.
  • Easy to use - Once the desired levels of calcium and alkalinity are achieved, all that is necessary is to add equal amounts of the two-part formulation according to manufacturer directions.
  • Safe - If used per directions, there is little chance of overdosing or shocking the aquarium inhabitants.
  • Supplementation can be easily tailored - Simply increase the daily amount when the aquarium inhabitants grow or when more animals are added.

Caveat

Though reliable and easy to use, there are a few shortcomings to the use of balanced calcium supplements.

  • Can be expensive for large aquariums - relative to other methods, it is the most expensive method for maintaining calcium over the long term.
  • Somewhat tedious - Each of the two-part balanced liquid supplements must be carefully measured out in equal amounts and added daily.
  • Problematic to correct - In the event where the alkalinity/calcium balance is distorted, it will be necessary to get things in balance through some other means which could exacerbate the situation.
  • Salinity may increase over time with regular use.

In the case of liquid compounds, it is even possible to automate their delivery by having dosing pumps administer the solution gradually over the course of the day.

Calcium Reactors as a Method of Calcium & Alkalinity Supplementation

As calcium supplementation has gotten more automated, one of the more sophisticated means of achieving and maintaining desired calcium levels is through the use of a calcium reactor. When used properly, this method provides a very precise means of maintaining calcium levels within a system. Other than some adjustments, calcium reactors offer very few problems.

These reactors, such as the CA+ Calcium Reactor, produce a calcium solution by dissolving a calcareous media (e.g., Aragonite Reactor Media) in low pH water. The low pH is achieved by introducing carbon dioxide into the reaction chamber. The rate of calcium supplementation is determined by the flow rate through the reactor chamber and the amount of the carbon dioxide dissolving the calcareous media.

Advantages

  • Automated calcium supplementation - When set up properly and used correctly, a calcium reactor can maintain or increase calcium levels with little maintenance.
  • Great for large reef setups with high calcium demands.
  • Low long-term maintenance cost - After purchasing and setting up a unit, the only items that need to be replenished are carbon dioxide and calcareous media.
  • Straightforward set up and maintenance.

Caveat

Calcium reactors, however, are not without some drawbacks.

  • High initial set up cost - These units are relatively expensive and in addition to the reactor itself, a proper setup will also require a carbon dioxide tank, CO2 regulator, needle valve and a pH controller.
  • Flow rate and carbon dioxide levels need to be manually set and adjusted at appropriate levels to facilitate proper calcium supplementation.

As long as certain precautions are taken and conditions are properly maintained, there is little problem in running a calcium reactor. Before turning on the reactor, the calcium and alkalinity levels should be tested and noted so that a baseline or reference point has been established. These levels will then be used to determine if the reactor is working at an optimum level.

As with any type of calcium supplementation, levels for calcium and alkalinity should be tested and monitored closely to make sure everything is working properly. To get the most out of your calcium reactor, the following aspects should be considered; proper media, size, flow rate, carbon dioxide level, pH level, regular testing, and long-term maintenance.

  • Media Selection - Some media may contain a lot of phosphate resulting in the release of phosphate as the media dissolves. Fortunately phosphate-free media, such as Aragonite Reactor Media, is now available.
  • Proper Size - Make sure the unit is appropriately sized especially for large reef systems with large quantities of SPS corals and coralline algae. An undersized unit may do a good job initially but over time, the reactor can no longer produce enough dissolved calcium to meet the calcium demands. It is now possible to find a calcium reactor for even the largest of aquariums.
  • Flow Rate - Flow rate should be set at 1-2 liters per hour, depending on the aquarium size, through the reactor. The flow rate can be increased or decreased to adjust calcium levels in your aquarium. If the flow rate through the chamber needs to be increased, then the CO2 bubble rate will also need to be increased. Keep in mind that the flow rate may need to be increased frequently in reef aquariums containing large quantities of SPS corals as the corals utilize more and more calcium.
  • Carbon dioxide level - The amount of CO2 should initially be set at 1-2 bubbles per second. Carbon dioxide levels need to be closely monitored so that excess CO2 is not introduced into the aquarium. Avoid excess CO2 in two ways: by using a properly functioning needle valve and bubble counter in combination with a pH controller, and by adding CO2 to a lightly aerated area in the aquarium.
  • PH level - The effluent from the reactor should be checked so that it reads a pH of approximately 6.5. For calcareous media to dissolve efficiently, the pH will need to be around 6.5. If the pH is higher, increase the amount of CO2 or reduce the water flow. It is usually better to adjust the CO2 level, since reducing the water flow will mean less calcium and carbonates flowing into the aquarium.
  • Testing - Calcium and alkalinity levels should be measured and the results should be at least equal to the initial levels (baseline/reference point) or they should be slightly higher. If they are lower, the flow and the CO2 bubble rate will need to be increased.
  • Long-term maintenance - Over time, a reduction in flow rate may occur due to buildup so the reactor, pipes, and valves will need to be cleaned periodically. Also, media other than Korallith may turn into a type of inert sludge in the reactor and reduce the amount of calcium being released even though the flow and CO2 levels look normal. The media should be removed and thrown out once or twice per year and the entire reactor should be cleaned out with mild vinegar and thoroughly rinsed. This will help keep the reactor working at an optimum level.

One of the latest advances is to use both a calcium reactor and a kalkwasser on aquariums that utilize large amounts of calcium. This combination maintains both calcium and alkalinity levels better than using just a calcium reactor with the added benefit of phosphate reduction and stable pH levels. It may be the optimum way of maintaining calcium levels in a large SPS tank.

Due to better understanding and the continuing development of calcium supplementation methods, SPS corals are now commonplace and their growth rates in some aquariums can exceed the rates seen in the wild. Understanding and implementing proper calcium and alkalinity supplementation may seem difficult at first, but with proper testing and patience, keeping these compounds at their proper levels will become quite simple.