Kalkwasser Question

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Hennie

My tanks Calcium consumption has increased rapidly over the last couple of months.

Reasons: New SPS and the eternal struggle between the coralline and my urchins.

I am finding that my normal dosing procedure is not enough. I dose 1 TSP with vinegar every night. This only increases the Calcium level by 5 - 20 ppm, to the previous night.

Can I increase my dosage and how much more would I be able to dose ?

I have a 500L tank - pH 8.4, Alk - 10 dKh, Ca - 360.

I would like to get the Calcium up to the 450 levels, but with my dosing procedure at present it might take me a couple of months and that is if I don't leave out a single day :p
 
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A successful reef aquarium inevitably reaches a level of calcium consumption where one cannot keep up with just dripping kalk, and one is forced to start using other methods to do so.

I dose 1 TSP with vinegar every night. This only increases the Calcium level by 5 - 20 ppm, to the previous night. Can I increase my dosage and how much more would I be able to dose ?
That would depend on the amount of water evaporation you have in the tank, how high the pH rises during the day, and the concentration of the actual kalk solution added to the tank.

Firstly, lets consider the concentration of the lime water solution, and how to increase it without increasing the pH too much:
  • Kalk (Calcium hydroxide or slaked lime) varies somewhat in density, but we can assume that 2 teaspoons per US gallon (3.8 liters) makes limewater that is about saturated. Saturated limewater supplies about 40 meq/L (14 dKh) alkalinity and about 800ppm calcium per liter.
  • Limewater supplies calcium in the form of calcium ions and alkalinity in the form of hydroxide ions. In order for this alkalinity to be used for calcification, it must be converted into carbonate alkalinity. This usually happens automatically when the hydroxide ions react with carbon dioxide in the water. The problem is that where the aquarium has a low fish load and/or a high rate of calcification, the amount of carbon dioxide which becomes available from respiration or the fish and/or from gas exchange with the atmosphere is less than that required to react with the limewater addition, and the tank's pH increases too much.
  • Vinegar increases the solubility of the calcium hydroxide in water, and it ultimately lowers the pH of the tank water by supplying carbon which is converted by the bacteria in the tank into (additional) carbon dioxide, and then used in the reaction to make more carbonates. Dr. Craig Bingman (who first described this method in detail) recommended that one should never add more than 12.2 ml of 'normal' food-grade white vinegar per liter of saturated lime water, and that one should start with only 25% of this concentration.
Secondly, lets consider the increasing of evaporation and the exchange of gasses:
  • More air flow over the water will result in more evaporation, which will increase the volume of lime water you can add every day.
  • Running the tank temperature a degree or two higher (if possible, but not higher than 28.5°C in my opinion) will increase evaporation, and it will increase respiration, thus increasing the amount of CO2 available to react with the kalk, thus helping to keep pH in check.
  • Having a brightly lit sump with lots of macro algae in it, running on a reverse daylight lighting cycle, will help to decrease pH swings and prevent the pH from dropping too low during the night.
  • Ensuring an adequate flow of fresh air to the tank will also help in keeping the pH stable.
If your calcium (and alkalinity...) demand is such that the 'spiked' lime water, increased evaporation and improved gas exchange still does not meet the demand, you will have to add more calcium and carbonate alkalinity (in a balanced ratio) by either running a calcium reactor, and/or adding chemicals, both topics being covered in detail in my other posts on this Forum.

I would like to get the Calcium up to the 450 levels
That's not necessarily where you want it - this will depend on the alkalinity as well. Remember that there is no advantage in having any more calcium than what can be converted into calcium carbonate by the corals, etc, and that can only take place in a fixed (balanced) ratio. As an example, it would be a waste to have the calcium level higher than 420ppm if the alkalinity is 8.2dKh, or higher than 410ppm if the alkalinity is 7.0dKh. Keeping the calcium at 450ppm would require an alkalinity of about 12.5dKh, which is pretty difficult to maintain unless you are running both a calcium reactor AND dripping lime water.

Hennie
 
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Hennie

Thanks for an excellent explanation. using your figures here I will start ramping up my dosing and I am sure I will get the desired effect and Ca level.
 

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what a brilliant response, thanks Hennie, i think you answered many questions in that reply.
 
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I would suggest that you correct the calcium and alkalinity levels to close to where you would ultimately like to keep them with chemical additives first (see Chemical equivalents - Hennie's Corner) and then try to maintain the levels with the spiked lime water - it will be a lot less frustrating this way :)

Just keep one further caveat in mind - using (or increasing) vinegar to 'spike' the lime water can result in an increased growth of diatoms, especially if your water's nutrient levels are above the 'minimum'.

Hennie
 
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I sit possible to dose into the overflow, or will the skimmer take the Kak out of the water column ?
 
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I presume you meant to say 'kalk' - the skimmer IS supposed to remove the 'kak' :)

To answer your question, though - dripping into the overflow will be OK - in fact, that is how I'm doing it, and I don't have any problems with the skimmer pumps (obviously, one must clean the pumps regularly in any case, and a soaking in vinegar every 6 months or so won't be a bad idea...)

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I presume you meant to say 'kalk' - the skimmer IS supposed to remove the 'kak' :)

To answer your question, though - dripping into the overflow will be OK - in fact, that is how I'm doing it, and I don't have any problems with the skimmer pumps (obviously, one must clean the pumps regularly in any case, and a soaking in vinegar every 6 months or so won't be a bad idea...)

Hennie
:biglaugh: Sorry I meant Kalk. Thanks it seems like a really good spot to dose to make sure all the slurry is dissolved probably.
 
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Since I have been dosing with Kalk, my Ca levels have increased -great.

I have also had an increase in Alk - 6 meq/L is this level OK ?
 
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Since I have been dosing with Kalk, my Ca levels have increased -great.

I have also had an increase in Alk - 6 meq/L is this level OK ?
That is something like 17 dKh - a little too high for comfort (good range is between 7-12 dKh). It is likely, however, that your reading could be false. What test kit are you using, and are you using vinegar with your kalk? If so, the vinegar can cause a false high reading on certain test kits (those with a lower titration 'end point'). Certain types of salt contain elevated levels of borate, which will also cause a false high reading.

What is your daily pH fluctuation? If between 0.2 and 0.4 between lights on and lights off, it's pretty unlikely that the alkalinity is so high...

Hennie
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That is something like 17 dKh - a little too high for comfort (good range is between 7-12 dKh). It is likely, however, that your reading could be false. What test kit are you using, and are you using vinegar with your kalk? If so, the vinegar can cause a false high reading on certain test kits (those with a lower titration 'end point'). Certain types of salt contain elevated levels of borate, which will also cause a false high reading.

What is your daily pH fluctuation? If between 0.2 and 0.4 between lights on and lights off, it's pretty unlikely that the alkalinity is so high...

Hennie
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Hi Hennie

Seachem kit

I am using vinegar

Ph fluctuation is very small, 0.1

I will re-check the reading with a Tropic Marin kit that reads in dkH
 
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13 dkH on Tropic test

I will check later today and see if this changes as I did double dose kalk and vinegar last night.
 

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Can you confirm what your alkalinity is sitting at Warr?
 

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