Calcium Hydroxide

[macpegg]

Is this is a good way to increase calcium levels? im starting to use it.. And gradually im increasing the calcium, without increasing the PH obviously. I`ve not heard many people bother with it.. Is this because of specific reason?.. thx

 

[Navarre]

Now i might be wrong here as im not good with chemical names. I think Limewater is Kalkwasser. (German for it i assume?) If it is Kalk then its used a great deal in th Marine community with great effects.

 

[Donya]

Yep, Kalkwasser is Ca(OH)2 calcium hydroxide, limewater (although just plain "lime" is calcium oxide, CaO). I had a really good page I was reading a few months ago about the stuff, but I can't find it now darnit.

 

[macpegg]

Yeah ya both correct. Trying to dose a 680 ltr tank is proving difficult. taken me ages. to get it right but once its there i`ll just have to maintain it with added water when it evaporates. so far so good..

 

[Ed4567]

I think that adding calcium hydroxide will, while increasing your calcium levels, also increase your alkalinity (if you're interested in the chemistry it's because the OH group will react with dissolved carbon dioxide to form a carbonate ion).

You need to know the alkalinity in your tank before making any corrections. This article goes through the solutions:
http/www.advancedaquarist.com/issues/nov2002/chem.htm

 

[macpegg]

yep. i`ve read the the alkalinity will rise, which is why im adding the mix at night when the PH drops slightly. I`ll be taking me time adding it, over the coming week. Ive never seen me corals look so damn happy and flourished. im well impressed!

 

[superman]

When using lime water it is important to be aware of its abilities. It is best to be used to sustain calcium levels, not to raise calcium levels. It is best to raise calcium levels with products like turbo clacium made by kent, or biocalcium by tropic marin. After reaching acceptable calcium levels, lime water is great at sustaining those levels once the correct dosage is determined through dilligent testing. A side note-alkalinity will not be sustained the same as calcium when using lime water, so extra buffering of alkalinity will be needed over time.

 

[macpegg]

I`ve been topping up Kalk with r/o and can see a def improvement not just with the testing.. But i feel that im wasting the kalk as there is quite a bit left over sitting at the bottom..

So am i supposed to put the kalk in with the r/o until it just starts to sit at the bottom until it dissolves? or is when it starts to sit it mean that no more can be dissolved?

 

[Donya]

The reaction's gone wrong when stuff starts to fall out (or I guess it's become saturated...but that would seem pretty hard to do). It's calcium carbonate you have precipitating out at the bottom...

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.

(from http/www.reefscapes.net/articles/breefca...alkwasser.html)


I also read this:

It is important that the calcium hydroxide not come in contact with atmospheric carbon dioxide because insoluble calcium carbonate is formed which precipitates out of solution and does not contribute to the maintenance of the pH nor does it provide readily usable calcium to the invertebrates.

(from http/avdil.gtri.gatech.edu/RCM/RCM/Aquar...umReactor.html)

But, that seems a little strange to me. Isn't kalkwasser sold as a powder? Or is it already in solution?


EDIT: btw I have to disagree about that last quote's statement about inverts. CaCO3 may be unusuable to corals and other benthic animals that don't move around for food (clams and such), but snails, shrimp, etc will actually eat calcium-based solids, including that one and others.

 

[macpegg]

Yip its a powder.. So me thinking that the powder that is left is because no more can be dissolved in the water is wrong?

and also should i then add co2 to the mix?

 

[Donya]

To be honest I can't find any references to what happens with a saturated Ca(OH)2 solution. However, the odds of it being saturated are pretty low. Say you have a bucket of water and a cup of water, pure H2O in both. You saturate the cup with salt, and then add more until you have a salt deposit at the bottom of the cup of water: no mroe salt can dissolve int he cup. Then, you add the cup of oversaturated solution to the bucket of pure H2O. Suddenly that excess salt has a place to go and poof...no more salt at the bottom. So, if you have a solution with no precipitate in the bottom (barring supersaturation), add it to a bigger volume of the solute, and THEN see a precipitate, there is something else going on other than just saturation/dissolution. Most likely you have a CO2 reaction issue, or a related reaction that is producing CaCO3 by some other means.

 

[macpegg]

i may sound stupid here.......

So the precipitating calcium carbonate at the bottom is what should be in the tank? or if its precipitating the whole mix is wrong?

or is it beacuse the r/o machine life has expired and need the filters changed?

to be honest im lost..


The instruction state im sure that if it leaving powder at the bottom, then ive put too much in.

its not helping that i`ve had a crap day at work.. lol

 

[Donya]

Hang on...is what you have Kalkwasser or just Kalk/lime? I just had a bonehead chemistry realization: Ca(OH)2 has to be in solution already, so if you have a powder, it surely must be something other than that. You can take calcium oxide, CaO, add it to water and produce Ca(OH)2. Perhaps that's what you have? If that's the case, you may have this going on:

CaO(s) + CO2(g) -> CaCO3(s)

You could always try the vinegar-using solution listed on the first one of the pages I quoted from before. I havn't done it myself but hey, if it gets rid of the white powder and the Ph tests out ok, it's worth a try

 

[macpegg]

the kalkwasser powder im using. the instruction did state about using vinega has makes it clumpy i think its said.....

to be honest the instruction were pretty rubbish, didn`t really explain how to mix it, just said mainly don`t let it touch ya hands or clothes.

With the vinegar soloution, do i need r/o for that.. or just mix directly with the powder straight from the tub?

 

[Donya]

I doubt the mix is wrong. Calcium carbonate forming on the bottom is not what you want though...you want to see a clear solution, or at least one that's free of stuff at the bottom. The calcium part of calcium hydroxide (what SHOULD form for you) should remain free in the water, and the hydroxides should break off and get converted to water. When you add the powder, does it just clunk to the bottom and form a precipitate, or does a noticable volume dissolve?

EDIT: we're are typing at the same time lol posts are getting out of sync. I've never done the vinegar solution, but it describes what to do here: http/www.reefscapes.net/articles/breefcase/kalkwasser.html

I don't know about the vinegar causing clumping, since I havn't tried it myself. You could always try with a small volume though and see what happens. It's possible that if the whole amount just goes straight to the bottom, that you don't have your original calcium oxide (CaO) or calcium hydroxide (Ca(OH)2) chemical anymore in the bag/box. Is the stuff you're using a brand, or just labeled as kalkwasser powder?