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CA and KH additives


Tom Gunner

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Due to to fact that I'm beginning to add some SPS coral to the tank, I want to raise my levels of Calcium to around 400-420ppm and kh around 9kh.

I've been adding small amounts of kalk to every other topup water-bottle to kick start the coralline successfully, but I was wondering what peoples recommendations where for maintaining a good CA and KH level on a tank of my size (tiny) with (surprisingly) no calcium reactor etc.

My shortlist from initial research would favour:

Seachem Reef Advantage Calcium & Seachem Reef Builder - This was a popular combo in Canada, and I know a couple of guys who use this with success.

Reef Success Calk - I think a couple of people have recommended this as an all in one CA and KH additive.

Kalkwasser - Using this along with baking soda to keep the KH in check.

Any advice would be greatly appreciated - my knowledge in CA and KH management is rusty at best.

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Any of the above are fine, they're all good. If you add kalk only, you may find that after a while your alkalinity & calcium get a little out of balance with each other. If that happens, add one of the other two to balance things up again.

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Baking soda (Sodium Hydrogen Carbonate) does alkalinity, and therefore effects pH. Initially it can lower it, as carbonate / hydrogen carbonate equilibrium is established, and CO2 is released. This effect is only temporary.

Hey Layton, what's your recommendation with regards to baking soda? I normally mix 4L of Kalkwasser at a time and use it in 2 days. Should I add a tsp of baking soda to every other mixture? Every 4th mixture? Do I keep the baking soda clear of the Kalkwasser altogether and alternate mixtures of Kalkwasser with something like Reef Success Ca? Do I add baking soda to the Ca mixture? Basically, I suppose I am asking for an ideal supplementation regimen that will keep my KH, pH, Ca, and Mg levels roughly constant.

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Well, kalk should deal to the calcium and alkalinity in one.

Having said that, if you have a large bacterial sink of carbon in the tank (like a DSB), alkalinity can be used at a faster rate than calcium. This is when you need to supplement with baking soda.

Alternatively, if your evaporation rate is not high enough that kalk can't keep up with BOTH calcium and alkalinity, then you need to look at a two part system using calcium chloride and baking soda, to deal with calcium and alkalinity levels, or alternatively run a calcium reactor.

Magnesium is a separate thing. It's tested for and adjusted using Magnesium Chloride.

pH takes care of itself if alkalinity is in line (and atmospheric CO2 levels around the tank are normal)

Layton

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Layton - I've been adding Distilled White Vinegar to the Kalk mix on the recommendation of this Reefscapes article. Any thoughts on his methodology? Agree - disagree?

When Calcium Hydroxide solution (Kalkwasser) is slowly dripped into your aquarium, it captures free Carbon Dioxide present in the tank water and converts it to Bicarbonate ions (which is a good thing), like this:

Ca++ + 2(OH-) + 2(CO2) <==> Ca++ + 2(HCO3-)

If you drip too fast or if there is not enough Carbon Dioxide available in the water, your shiny new Bicarbonate ions will be converted to Carbonate ions (a bad thing), like this:

Ca++ + 2(OH-) + 2(HCO3-) <==> Ca++ + 2(CO3--) + 2 H2O

The Carbonate ions formed will make the Ca++ you are trying to add to your tank get wasted by the useless precipitation of Calcium Carbonate -- the white stuff you are seeing.

So, too rapid addition of Kalk may actually cause the Calcium and Alkalinity in your tank to go DOWN instead of UP (a bad thing), like this:

Ca++ + 2(HCO3-) + Ca++ + 2(OH-) <==> 2 CaCO3 + 2 H2O

In the above reaction, a Calcium ion and two Bicarbonate ions from the aquarium combine to form solid calcium carbonate -- the white stuff you are getting in your tank, which is really just a kind of sand.

This can happen even with a slow drip of Kalk if there is not enough CO2 in your water -- something you can't easily control.

To avoid this, try mixing and adding your Kalkwasser like this: pour 15ml of 5% Acetic Acid (or ordinary Distilled White Vinegar from the grocery store -- same thing) into a 1 liter (1 quart) container. Dissolve 1/2 teaspoon of lab-grade Ca(OH)2 (or commercial Kalkwasser mix) in the Acetic Acid, and then dilute to 1 liter (1 quart) volume with either RO/DI water, or even tank water.

15 ml is more Vinegar than some people are comfortable with, but I use it constantly with no problems. There should be no sediment in the mixture, or just a little bit at most. You can let the sediment settle out if you don't like the white flakes in your tank. I just drip the liquid and the sediment both into my tank.

Dissolving the Kalk powder in the Vinegar first will accomplish several very good things.

First, it will get more Calcium ions (Ca++) into the solution because you are dissolving the Ca(OH)2 in an acid instead of water, and forming Calcium Acetate, which exists as a dissociated equilibrium of free Calcium ions and Acetate ions.

Second, the Acetic Acid (Vinegar) provides an equivalent of all the CO2 you need to avoid precipitating the newly-added Calcium ions as useless white Calcium Carbonate powder.

Third, after all the cool Calcium ion chemistry is over, the leftover Acetate ions from the broken-down Vinegar leaves you with free organic Carbon in the water that feeds the bacteria in your tank so that it converts more poisonous Nitrates to NO2 gas (a very good thing).

http://www.reefscapes.net/articles/breefcase/kalkwasser.html

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Looks to be a reasonably well written article, although the reactions are a bit simplistic. In reality, the calcium hydroxide does not completely stay as hydrogen carbonate ( HCO3- ) there is an additional reaction where the hydrogen carbonate is in an equilibrium with carbonate ( CO3-2 ).

Another benefit of the vinegar method is that the acetate forms a buffer, similar in effect to alkalinity, resisting changes in pH.

However, acetate is also used very efficiently by various types of important bacteria, including nitrogen fixing, and denitrifying bacteria, so the buffering effect is more than likely negligible.

Layton

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just a few questions if you dont mind me asking in this post :wink:

magnesium helps the groth of coraline....corect?

i understand that disolving Mg ribon in vinegar gives you a salt and a gas(magnesium......+hydrogen)

Metal + acid = Salt + hydrogen?

now my main question is would adding this Mg mixture to my tank be effective and safe to do so?

i would guess that the MG you reefers dose your tanks is in a different form,but am curious to see if i could dose some in this way?

Tim

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Well, yes you could do that without harm (as long as the Mg ribbon was not contaminated with other heavy metals)

But it would be an expensive and long winded way of doing it. Most people use magnesium chloride (or magnesium carbonate in a calcium reactor) it's a lot cheaper than ribbon, and a lot less messing around.

Layton

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