The Many Methods For Supplementing Calcium And Alkalinity - by Randy Holmes-Farley

[jrpark22000]

Info from Randy Holmes on R2R, good read especially for those who are new.


http://www.reef2reef.com/blog/the-many-methods-for-supplementing-calcium-and-alkalinity/

There is no aspect of reef aquarium chemistry more important than calcium and alkalinity. Many of my previous articles have described various aspects of these systems in detail. In reading those articles, aquarists will note one pervasive theme: that maintaining appropriate levels of each are very important.

Moreover, the easiest way to ensure that things do not go seriously wrong in adding these to the aquarium is to use additives that have balanced amounts of calcium and alkalinity. For purposes of this article, a balanced calcium and alkalinity additive is one that provides calcium and alkalinity in proportions that match that used by corals and other organisms to form calcium carbonate. Using this type of additive typically prevents overdosing (or under-dosing) of either of these two relative to the other. There are several advantages to using these combined methods, and those advantages as well as the methods themselves will be detailed below. It is hoped that this article will provide the information necessary for aquarists to choose an appropriate scheme for their specific needs. Such deciding factors as cost, complexity, impurities, and a variety of others things come into play in making a decision.

One can, of course, supplement calcium and alkalinity independently, using, for example, calcium chloride and sodium carbonate (or bicarbonate). Such methods are perfect for making corrections to calcium and alkalinity levels, but perhaps less than perfect for routine maintenance. While the regular use of such additives can work well, it frequently results in substantial imbalances between calcium and alkalinity. In a perfect world, with perfect test kits used perfectly and frequently by every aquarist, such additions would work out fine. All too often, however, they lead to imbalances, and sometimes to a roller coaster effect of high and low calcium and alkalinity as the aquarist struggles to get these fundamental parameters under control.

It is for this reason that I strongly encourage aquarists to select a balanced calcium and alkalinity supplementation scheme. There are, however, many such schemes to choose from. Towards the end of the article are two tables, one that outlines the cost aspects of each system, and one that summarizes some of the other differences. In the end, I don’t pick any one of these schemes as being best for all aquaria, although I do indicate what types of tanks each system works well for, and what types they don’t. For experienced aquarists, that will be all they need to make informed choices. For beginners, I’ve also included some guidelines at the end of the article that should help them integrate these various concerns and point them in the right direction for the type of tank that they are considering.

Aquarists should also not be averse to combining two or more of these schemes. In some cases there are substantial synergies that can be obtained from combining systems. Some of the more common combinations are also discussed below.

I will say that I do not believe that there are any other systems commonly used that are as good as these detailed here. So these choices should cover the systems that people ought to consider unless they have very peculiar situations (or something new is invented in the future).

I’ll also try to straighten out some misunderstandings that aquarists frequently have about them (e.g., issues around heavy metals, either added intentionally or present as impurities). I won’t, however, have space in this article to give exacting details about how each is to be used. In many cases, there are existing articles describing them.

The systems to be covered in this article are:

Limewater (aka kalkwasser), used in a reactor or not, and with vinegar or not
Calcium carbonate/carbon dioxide reactors (CaCO3/CO2 reactors)
Calcium carbonate used without a reactor
Calcium acetate
One part inorganic salt mixtures
Two/three-part liquid additive systems (DIY, commercial, Balling, etc.)
Water changes
For those wanting a discussion of my recommended levels of various parameters in a reef aquarium, including calcium and alkalinity, see:

Optimal Parameters for a Coral Reef Aquarium

And for further discussion of any of these issues, see my Reef Chemistry Forum at Reef2Reef here.

 

[jrpark22000]

More excerpts.

Limewater

Limewater (also known by the German term kalkwasser) has been used very successfully by aquarists for decades, and it is the system that I have used exclusively on my aquarium for 19 years. It is comprised of an aqueous solution of calcium and hydroxide ions that can be made by dissolving either quicklime (calcium oxide, CaO) or lime (calcium hydroxide, Ca(OH)2) in fresh water. The only inherent difference between the two is that if you add a molecule of water to quicklime, you get lime, and that a significant amount of heat can be generated when that happens.


Calcium Carbonate/Carbon Dioxide Reactors

Calcium carbonate/carbon dioxide reactors work by removing water from the tank, adding carbon dioxide to reduce the pH to about pH 6.5, and then allowing the more acidic water to dissolve solid calcium carbonate media that is present in a mixing chamber. The water is then returned to the tank with its extra calcium and alkalinity (bicarbonate):


Calcium Carbonate without a Reactor

In a previous article, I described in detail what one could do with calcium carbonate when not used in a reactor. In my opinion, the best use is to dissolve the calcium carbonate in fresh water, and use it as the top off water for the system. Other uses, such as adding particulate or milky products directly to the tank seem like poor practice to me (since particulate calcium carbonate likely won’t dissolve in a reef tank and may actually nucleate precipitation of additional calcium and magnesium carbonate from the water).


One-part balanced additive systems: Calcium Acetate

Calcium acetate is a product that has gotten relatively little publicity despite its apparent ease of use and the commercial availability to aquarists. In some ways it is similar to the combination of limewater and vinegar. When dissolved in water (fresh or salt), you have calcium ions and acetate ions. The acetate is rapidly metabolized by tank organisms to form bicarbonate, carbon dioxide, and water:


One-part balanced additive systems: Salt Mixtures

Another type of balanced one part additive is comprised of a simple dry mixture of sodium bicarbonate (or carbonate) and calcium chloride. Just as with the two-part additives described below, this type of system can be further formulated to have a natural seawater residue after removal of calcium carbonate. Tropic Marin’s Biocalcium seems to fall into this category, though its written descriptions are notoriously difficult to interpret. It costs about $18 for 510 grams (estimated to contain about 1800 meq of alkalinity), so that puts the cost at about $9.70 per thousand meq of alkalinity. It claims to add 70 trace elements to the tank, along with the calcium and alkalinity, but doesn’t specify amounts for any of them.


Two-part Balanced Additive Systems

There are now a plethora of two-part balanced systems for supplementing calcium and alkalinity, as well as DIY recipes that I have published and for which suppliers sell quality DIY ingredients. These are always liquid additives that you add equally to tanks to supplement both calcium and alkalinity. In the DIY version, magnesium is added to the aquarium as a third solution, although it need not be added especially frequently. The rational for this type of product is that the bicarbonate and carbonate that one might like to dose to supplement alkalinity are not readily compatible with the calcium that is also needed. So one portion contains calcium and the other contains the alkalinity. When a DIY is used, the magnesium sulfate in it is not compatible with either part, so it needs its own solution.


Balling Method

The balling method seems to be similar to the two/three part methods that are more common in the United States. There are different variations used by different people, and some (Fauna Marin) have three parts just like the DIY recipes, with a calcium part, an alkalinity part, and a magnesium part. One distinguishing feature of these is that they explicitly add a trace element mix to some of them (two additives into the calcium part, one into the alkalinity part, none to the magnesium part).


Water Changes

The one thing going for water changes is that it is hard to screw them up chemically (aside from salinity, pH and temperature). The bad thing is that it is impossible to replace more than a small amount of lost calcium and alkalinity to an aquarium in this way. Some salt mixes are available with higher than natural seawater levels of calcium and alkalinity, so it may suffice for the very lowest demand aquaria, but it cannot keep up with alkalinity in a tank with rapidly growing coralline algae and/or hard corals unless the amount changed is on the order of 20-50% daily. Calcium is somewhat easier to maintain with water changes, since some salt mixes have quite excessive calcium levels (500+ ppm), but even that is not enough for most aquaria.