Alkalinity, carbonate hardness, hardness, buffer, and other such terminology is often found in hobby literature. Frequently you will find them associated with references to the pH level. Explaining the exact chemical meaning of each, and the differences between them, is too elaborate a task for this short chapter.

What you need to be aware of is that the level of the buffer, or the carbonate hardness, as the latter is what is often measured to gauge the buffering capacity of the water - its ability to neutralize acids and withstand the tendency of the pH to want to drop - needs to be at a certain level for your tank and its corals and invertebrates to do well.

This is necessary for pH stability, as just indicated, but also because it definitely makes for a better environment for the corals (Peter Wilkens, 1979).

Many acids are continuously formed in the tanks water. Some are organic in nature, others are inorganic. Which ones, and why, is not really of concern to us here. What is important is that water conditions should be of a quality that prevents these acids from reducing the pH, or make the environment less acceptable for the corals. This means that you must keep the carbonate hardness, in this particular case, at a high level: between 12 and 18 dKH, preferably around 15. To convert dKH to meq/L (milliequivalents per liter), divide by 2.8. For example: 15 dKH is the same as 5.35 meq/L. I keep my own tank at even higher levels, but do not suggest you do too.

Hobbyists need not really worry about the details of the process that raise or lower the buffer. Commercial products are available that enable every hobbyist to maintain the KH or dKH level, as it is often called, at the correct magnitude.

KH generators come in tablets, powders and liquids. Here are, in my opinion, the advantages and disadvantages of each of them:

• Tablet form KH generators may contain only one of the many compounds that are necessary to adjust the carbonate hardness. One brand on the market contains nothing but sodium bicarbonate (baking soda) and a dye. Tablets may also contain binders to hold the powder together. This may result in your skimmer overflowing when you add them to the water. Check the one you use to ensure that it contains at least four, or even five compounds, and no binders. If it is not complete, resort to another form of KH generator.
• Tablets are of course easy to use, as all you need to do is drop them in the water and let them dissolve slowly. Such is a plus, but add them only after you have determined that they contain more than just baking soda (sodium bicarbonate), and make sure too that they do not contain "binders". If they do, and if you use them, watch that skimmer.
• Powdered form KH generators: most of the ones available are more complete, and thus contain all of the compounds necessary to raise the KH, and in those we tested, no binders were used. Make sure that they do not leach phosphates into your water. Checking for phosphate is easy. Add some of the powder to water that does not contain phosphates, let the mixture stand for a few hours, and then use a phosphate test. If the product adds phosphates, do not use it. Phosphates will, invariably, lead to the appearance of micro-algae which you will have a very hard time eradicating, even if you use products such as Ridalgex and Micro-algae Controller, because every time you use the product, you are, in essence,

re-adding phosphates as well, and the algae will reappear.

• Liquid KH generators are the ones that I personally prefer. They are easy to add, and do not raise the dKH too quickly in too short a period of time. They also contain all the required compounds to raise the KH hardness, uniformly and evenly. Sediment will be present in most liquid KH generators. Such is normal. All you need to do is shake the container to mix all the ingredients up again.

Some, such as calcium carbonate, will remain in suspension and will not dissolve. They are added to the tank in that manner each time you dispense a small amount of KH generator. Such is also the correct way to add these compounds. If your KH liquid contains chunks of matter at the bottom, some of the compounds may have come out of solution because of a temperature drop. To redissolve them quickly, warm up the compound a little, and shake the container.

Any time you affect the KH level of your tank by adding tablets, powder or liquids, you will need to check the carbonate hardness itself by using a test. Such tests are now widely available in the hobby. You must verify that you are not raising it too much on one hand, and enough on the other. Suggestions as to how high the KH should be vary greatly depending on which author you read, and also depending on how much that author has experience with reef tanks.

Since prior to 1986 reef aquariums were very rare, most texts you will find suggest levels that are intended for fish-only aquariums. Good sources of reference information include: Peter Wilkens, Guido Hueckstedt, Albert Thiel, and Klaes Aquaristik's literature and articles in hobby magazines.

My own recommendation is, and has been since 1985, that you raise the KH slowly to a dKH of 12 minimum, and 18 maximum, with 15 being the level I would recommend you keep your tank at. dKH stands for German degrees of hardness.

Why this "German" in the name? Because there are several methods used to express the hardness, and dKH is a very common one, especially all over Europe. In North America hardness is expressed in either meq/l, milliequivalents per liter, or in ppm, parts per million.

Converting from one to the other is easy. dKH divided by 2.8 equals meq/l. dKH times 18.9 equals ppm. meq/l times 2.8 equals dKH, etc. For example a dKH of 15 is the same as 5.35 or 283.5 ppm, a dKH of 12 is the same as 4.28 meq/l etc.

Pet Stores also sell "alkalinity" tests; such tests can be used as well. Although they are technically speaking different from carbonate hardness tests, for our purposes the difference is so minimal that it can be neglected. Aquarium Systems make such an excellent test.

You must adjust the KH slowly if it is too low. Do not make rapid changes in the aquarium. In fact, as already pointed out, this remark applies to any condition in the tank. No parameter should be changed too quickly. Such would stress the fish and the invertebrates, and can be one of the many causes leading to the appearance of parasitic outbreaks, or the corals not looking good or as healthy as they normally should.

Is there too high a KH level? Research through aquarium literature indicates that very little has been written on the subject, and I can therefore only go by my own experiments which indicate that 24 dKH is about the highest you will want to go, and that at 29 dKH most tank inhabitants react very negatively. Anemones close up and may die off, corals close, etc. Although I have always recommended very high KH levels, and still do, keep the level in your tank around 15 and not over 18 dKH. You will notice a marked difference in the way your tank looks when you do.

Because all hard corals require more than just bicarbonates, also called hydrogen carbonates - they need carbonates as well - you must also use another additive when adjusting the KH: Kalkwasser, or limewater, which greatly enhances the availability in the water of calcium carbonate. Corals precipitate calcium carbonate to build their hard outer skeletons.

According to certain sources and texts, orthophosphate interferes with this process. This makes it even more important to ensure that you do not add any phosphates, in any form, to your tank. If corals cannot perform that function efficiently, they will die on you in a matter of weeks or months at the utmost. At best they will look in sad shape, dwindling away, and becoming smaller and smaller, or not opening up as much as they used to.

Kalkwasser is not widely available but can be ordered from TAT in one gallon sizes. You must do so if you wish to keep corals for any length of time, and want to see them thrive. At the time of this writing one gallon sold for $16.00, plus shipping, or order Kalkwasser from your local dealer. Get them to order it for you if they do not keep it in stock. TAT is mainly in the distribution to stores business, not in mail order. Such is also the reason that they do not accept credit cards.

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