How much kalkwasser to dose???

G

GPCRalph

New member
Hello,

Can someone help clarify how to set-up and dose kalkwasser on a Kalk reactor connected to auto? Your input/experiences would be greatly appreciated!
I recently set-up a system where the tank ~80-90 gal and my goal is to maintain a mixed reef. I have been reading and debating on which method to use for maintaining calcium/alkalinity and have settled on using a kalk reactor connected to my ato. However, I am confused on the dosing. When I read the forums I see posts about "tablespoon sized" doses per gallon of freshwater. When I read the directions on my Kalk reactor it recommends ~0.5 cup (~biweekly); their recommendations are based on how much water is replaced per day/week in the system. Even still, there is a very big difference in the dosing here.
Am I to assume that the much higher dose on the Kalk reactor is because only a finite amount of calc/alk will dissolve into the water column and so the actual dose is the same in both scenarios because as new top off water goes in, it will continue to mix and reach the same effective concentration? But what if my system is new and only has a few corals? Will this does be too high since it is replenishing all of my evaporated water/day?

:headwally:
Thank you!
 
start with a 1/4 cup in the reactor, then test alk, ph and calcium after a day or so. Alk can rise very rapidly with Kalkwasser as well as pH.. don't ask me how I know this. I go easy on it because ATO is totally dependent on your evap rate, therefore kalk dosing is also dependent on your evap rate, not by your tank's needs. I do it.. and I know it's not ideal, but it works. Just go easy in the beginning. I usually add one tablespoon of kalk to my TLF reactor once per week. Currently with this method, my pH hovers around high 7s to 8.1 ish. Calcium is close to 500 and alk is at 9.

Edit: just want to mention that I do occasionally dose calcium and magnesium separately when I don't want to raise Alk..
 
I put kalk in my topoff ro/di. 2 tsp per gallon of ro/di. That's all that CAN dissolve. Residue will dissolve later.
Stir once on adding, never again. You do not want white water going into your tank. Should be nearly clear.
I had a reactor and tossed it---the topoff works better without it.
If you should get an overdose it's pretty harmless: ph self-corrects very fast, but if it throws the ph badly, a teaspoon of bar soda per 50 gallons of tank can help. No more than that.
 
If you are using a still reservoir, only 2 tsp per gallon will dissolve, as has been stated. A Nilsen reactor has a stirring mechanism and an automatic method for adding fresh water, so adding a large amount of Kalk is useful. I'm guessing you have a stirrer in your reactor?
 
Calcium hydroxide saturation? My question is why do many reefer's suggest 2tsp. per gal.? Many web.sites(Wikipedia) for example state 1.5 g/l at 25c which comes out to about 6 grams per gal. a little over 1 tsp.
 
I get about 6 grams per gallon for solubility at 25 C, as well, but my search returned a range of density levels, but none as high as your number. 2 tsp seems like a reasonable guess, but weighing would be more precise. Are you just using the density of water as an estimate? I get something like 0.6 g/ml, or about 10 ml soluble per gallon, from this site:

http://www.anval.net/downloads/bulk density chart.pdf
 
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bdsage said:
Calcium hydroxide saturation? My question is why do many reefer's suggest 2tsp. per gal.? Many web.sites(Wikipedia) for example state 1.5 g/l at 25c which comes out to about 6 grams per gal. a little over 1 tsp.
Click to expand...

The extra calcium hydroxide in the 2tsps per gallon is to insure the maximum saturation state is maintained ;given the precipitation of calcium carbonate as the hydroxide forms CO3 with the CO2 in the water or stirred into it from the surrounding air when mixed in an unsealed container .
 
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6 gr of calcium hydroxide mixed in 1 litre of RODI produce a fully saturated limewater. Your pH monitor should show ~12.4 at 25C when its probe is dipped in this solution.
 
OP: To answer your question more specifically, it doesn't matter how much kalk you put in your reactor within a certain range. Because of the way a kalk reactor works, there's a very large excess of kalk in contact with the RODI in the volume of the reactor. This kalk will (ideally) dissolve as it can to produce a fully saturated solution as it's fed into the tank with the ATO water.

The "within a certain range" means that if you add only a little bit of kalk (say, a couple of teaspoons), then the water going through the reactor will deplete the available kalk powder in a rapid manner - you'll get a fully saturated output for a little while, and then only RODI. There will be some visible solid in the reactor, but this is insoluble calcium carbonate formed by the reaction of some of the calcium hydroxide in solution with dissolved carbon dioxide in the make-up water.

If you put too much in a kalk reactor, then the force of the ATO pump will cause a slurry to be formed that extends through the entire reactor without a clear, settled layer on top. You'll then be dosing this slurry to your tank, which can cause a rapid increase in pH, and possible production of a "snowstorm" of precipitated calcium carbonate in the tank (as well as magnesium hydroxide, if the pH goes way up).

So the amount to use requires a bit of experimentation, and you may have to adjust your ATO pump's rate to allow the material in the reactor to produce a clear layer of saturated kalk solution in the top of the reactor, that then overflows into your tank.

With respect to whether dosing fully saturated kalkwasser to your tank is appropriate, that depends on the calcium and alkalinity demand of your tank and its evaporation rate. You can establish this by setting your kalk reactor up as described above, and test your tank water's calcium and alkalinity demands over the next several days. If your Ca and Alk increases above your desired range and/or you start to see precipitation on your pumps, tank walls, etc..., you'll need to dial back the amount of kalkwasser going into the tank. The only practical way to do this and still keep using your reactor is to buy an adjustable peristaltic pump to feed the kalk reactor - by "adjustable", I mean actually adjustable by means of a rheostat on the pump that controls the rotation rate (and therefore the flow rate), or a fixed-speed peristaltic that you then turn on and off with a timer or aquarium controller.
 
Deltec's advice is to put 150 gr of calcium hydroxide into their kalk stirrer's body. This is the device I follow while using my Deltec kalk stirrer. 150 gr lasts about 1 calendar month based my tank's evaporation rate. This duration inevitably varies depending on evaporation rates.
 
Thanks guys for all info...i only really started searching ''calcium hydroxide saturation'' because iv only been dripping kalk at 1/2-3/4 tsp per gal(despite several growing sps colonies and a lot of coralline) and this has kept my alk steady at 7-7.5 and my water topped up. my evap is about 1/3 gal per day, no ato (low tech system...) any way i thought i was at about 1/4 saturation(until i searched...) hence i would probably never have to change the low tech way(kalk drip) of dosing cal./alk.on my 40 gal system. soooo am i some where in the ball park in my thinking or lack there of...?








0
 
Agree with dkeller.

In my case, Kalk alone is not enough to meet my tanks requirements, so I have my Kalk stirrer setup to deliver saturated solution all the time. I monitor the pH of the effluent to ensure this. Easy enough to setup a Kalk reservoir so that the slurry does not get into the tank so I tend to add a 1/2 cup of power at a time, which translates to approximately a week of saturated line water.
 
bdsage said:
soooo am i some where in the ball park in my thinking or lack there of...?
Click to expand...

Most reef tanks eventually do require more than saturated kalkwasser as the entirety of make-up evaporation eventually. Unless, of course, the tank's all soft corals. If you simply continue to monitor your calcium and alkalinity at least once a week, you'll know when you have to supplement with 2-part dosing or a calcium reactor.
 
Thank you all for your responses. This helped me organize my thoughts on how to dose. I am using an Avast Marine Kalk stirrer with an Aqualifter pump feeding RO water into it.

If I understand correctly, either way you do it, you are essentially dosing a saturated solution but what we can control is how much of the solution we dose and how quickly. If you put less powder into the reactor then the saturated water in the Kalk reactor will last less time. So then the overall dose will be less because the solution will dilute sooner.

Thank you again.

-R
 
Limewater from Kalk reactors tends not to be fully saturated, although I'm not sure why. A number of people have checked their reactors and found that to be true, though.
 
bertoni said:
Limewater from Kalk reactors tends not to be fully saturated, although I'm not sure why. A number of people have checked their reactors and found that to be true, though.
Click to expand...

It is probably because most reactors are not properly sealed. The moment you stir calcium hydroxide in water, limewater's potency start to decline until some sort of crust seals the water surface.

The potency of limeweater in my reactor (Deltec KM 500) on day 1 is about 10.2 mS (i.e. fully saturated). After 30 days of using up 150 grams of lime, the potency drops down to around 7.5 mS.

I personally can live with that given the convenience of dosing limewater without any effort on my part (except topping my reactor once a month). Since drop in alkalinity and calcium as up a result of drop in the potency of limewater is lender month.gradual, my corals do not react in a negative way. FWIW, my alkalinity seems to swing between 6.5 dKH-7.5 dKH within a calendar month.
 
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