Using Kalkwasser to raise Calcium in the Reef Aquarium

Kalkwasser is the German word for “lime water.” Kalkwasser is an industry trade name for Calcium Hydroxide. The terms “Kalkwasser,” “limewater,” and “calcium hydroxide” all mean the same thing in the reef aquarium hobby.

We need to be cautious while working with any calcium compound because they are caustic. Do not let the powder contact your skin, do not inhale it, and always keep it out of children’s reach!

A Kalkwasser solution used to raise calcium in the reef aquarium can be made by using RO/DI or distilled water and adding calcium hydroxide (Ca(HO)2). You can find calcium hydroxide in powder form at most hardware stores or garden nurseries, just  be sure the compound you find does not contain any Phosphates!

Preparing and mixing the kalkwasser solution isn’t all that difficult, once mixed you need to cap it so no carbon dioxide can enter the container.  If carbon dioxide is allowed to enter the mix, it causes calcium carbonate to form on the bottom as an un-dissolved white slurry or sludge. Do not use this sludge and never allow it to enter your aquarium. It is recommended you remove the settled calcium carbonate from the container before each new use. Each time you open the container the kalkwasser mix gets exposed to more carbon dioxide, and more calcium is lost adding more calcium carbonate slurry to settle on the bottom.

Mixing kalkwasser to raise calcium for reef aquariums can be accomplished by using this guideline: one teaspoon up to one tablespoon of kalkwasser per one gallon of RO/DI or distilled water. Mix it so that all the powder is in suspension then cap the container. It’s a good idea to drip the kalkwasser mix slowly to the reef aquarium at night so the pH doesn’t rise to high. Kalkwasser itself has a high pH of 12 and higher, so be careful when dosing this mix and always test your water parameters before and after dripping any additives. Drip the kalkwasser within a day of mixing, it will slowly lose it’s effectiveness as the days go on. I mix up a 5 gallon jug worth and drip my kalkwasser over a 2 day period then I rinse out the jug and mix up a new batch.

Setting the proper drip rate depends on your reef aquarium setup and the total water volume your aquarium has. For my small aquariums 30-50 gallons, about one drip per second is sufficient and should not cause any sudden fluctuations in your reefs pH. For larger tanks kalkwasser can be dripped at a faster rate as long as you monitor the pH.

There are some articles on the web that describe how you can make your own kalkwasser drip container out of water bottles, milk jugs, glass jugs, etc… All you need are a few inexpensive items like the following:

·         Air line tubing

·         Water bottle or jug with an air tight lid

·         Rigid air line tubing

·         Airline valve kit for adjusting your drip rate

Some benefits of dripping Kalkwasser to raise calcium in the reef aquarium:

Benefits are:

It adds/replenishes calcium that is needed by most of the creatures in the reef aquarium.
It encourages the growth of pink and purple coralline algae.
It helps to keep the pH constant.

Awesome inventions and ideas I’ve thought of to enhance my fish tank inexpensively.. Send me your ideas… By the way, the sand is better (in my opinion and experience) than gravel because the waste and food remain on the top of the sand, rather than mixing with it like it does with gravel. I DON’T recommend you using silica sand! I tried it for two months and it made some of my fish sick and killed others. And as soon as I put the regular sand in the tank the fish began to get better. They had fin rot with the silica sand and some acted ill..
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