Avast Kalk reactor layer on top of reactor
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Dennis Cartier
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You should leave it as the layer on top is preventing CO2 from reaching the kalk solution and causing it to precipitate (which is what the top layer is).
Randy Holmes-Farley
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It is calcium carbonate.
What is that Precipitate in My Reef Aquarium? by Randy Holmes-Farley - Reefkeeping.com
Precipitates on Top of Limewater
The precipitate that forms on the top of limewater is calcium carbonate (Figure 5). Limewater is high in calcium (about 800 ppm at saturation) and is very high in pH (pH 12.54 at saturation), meaning that it contains a lot of hydroxyl ions (OH-). When carbon dioxide from the air encounters the water, it hydrates to form carbonic acid:
(1) CO2 + H2O → H2CO3
Then, if the pH is above 11, as it is in limewater, the carbonic acid equilibrates to form mostly carbonate:
(2) H2CO3 + 2OH- → 2H2O + CO3--
It is the carbonate that we are concerned with in the formation of insoluble calcium carbonate, both on the surface of, and inside, the limewater:
(3) Ca++ + CO3-- → CaCO3 (solid)
The result of this reaction is visually obvious. The calcium carbonate can be seen as a solid crust on the limewater's surface that has been exposed to the air for a day or two (do not bother to remove this crust; it may actually be protecting the underlying limewater from further penetration by carbon dioxide). The formed solids also settle to the bottom of the container, and can, in fact, form down inside it. Since solid calcium carbonate is not an especially useful calcium or alkalinity supplement, this reaction has the effect of reducing the limewater's potency. With sufficient exposure to air, such as by aeration or vigorous agitation, this reaction can be driven to near completion, with little calcium or hydroxide remaining in solution.
This reaction is the basis of the claims by many aquarists that limewater must be protected from the air. It is also the basis of the claim that limewater reactors (Nilsen reactors) are to be preferred over delivery from still reservoirs of limewater. Neither of these claims, however, stands up to experimental scrutiny, as I showed in a previous article.
What is that Precipitate in My Reef Aquarium? by Randy Holmes-Farley - Reefkeeping.com
Precipitates on Top of Limewater
The precipitate that forms on the top of limewater is calcium carbonate (Figure 5). Limewater is high in calcium (about 800 ppm at saturation) and is very high in pH (pH 12.54 at saturation), meaning that it contains a lot of hydroxyl ions (OH-). When carbon dioxide from the air encounters the water, it hydrates to form carbonic acid:
(1) CO2 + H2O → H2CO3
Then, if the pH is above 11, as it is in limewater, the carbonic acid equilibrates to form mostly carbonate:
(2) H2CO3 + 2OH- → 2H2O + CO3--
It is the carbonate that we are concerned with in the formation of insoluble calcium carbonate, both on the surface of, and inside, the limewater:
(3) Ca++ + CO3-- → CaCO3 (solid)
The result of this reaction is visually obvious. The calcium carbonate can be seen as a solid crust on the limewater's surface that has been exposed to the air for a day or two (do not bother to remove this crust; it may actually be protecting the underlying limewater from further penetration by carbon dioxide). The formed solids also settle to the bottom of the container, and can, in fact, form down inside it. Since solid calcium carbonate is not an especially useful calcium or alkalinity supplement, this reaction has the effect of reducing the limewater's potency. With sufficient exposure to air, such as by aeration or vigorous agitation, this reaction can be driven to near completion, with little calcium or hydroxide remaining in solution.
This reaction is the basis of the claims by many aquarists that limewater must be protected from the air. It is also the basis of the claim that limewater reactors (Nilsen reactors) are to be preferred over delivery from still reservoirs of limewater. Neither of these claims, however, stands up to experimental scrutiny, as I showed in a previous article.
Randy Holmes-Farley
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How long did it take that layer to form?
You sure air is not getting in soem other way? An o-ring level of air seal is not usually not needed.
Are you aerating the source water before use?
You sure air is not getting in soem other way? An o-ring level of air seal is not usually not needed.
Are you aerating the source water before use?
Ed Kaz
Community Member
Hi Randy... Thanks for taking the time to reply. I am trying something different (after 20 some years trying to get corals to grow . Even softies ) that goes against reef chemistry and having high alk levels(not by choice) and raising PH. I have tried running air from outside to protein skimmer (old school E.T.S.S.) to raise PH (did not do anything)and had the ICP test done but nothing showed up as "Bad"? With the kalk reactor I maintain a stable 8.15ph but my alk is @ 14.5dkh (and has been over 14dkh for 6 months). The tank is doing fantastic with the corals that are in there! My PH has always been low @ 7.7-7.8 in the past and with the help of kalk I was able to raise it up.
Tank is 180gal w/100gal refugium (growing some type of grape algae)
PH--8.15
Alk --14.5dkh
Cal---450
Mag---1380
Nitrate --65 (dropping with help of a korallin denitrator).
Phos---.2
Anyway getting back to kalk reactor .. It's fed from a 65gal RO/DI container with a Ecotech versa for my make-up water.
Using BSR Kalkwasser with about1pound in reactor that has been untouched for months. I test weekly PH from output to insure12.5PH in reactor. Kalk is getting low and I will need to refill reactor soon and need to remove layer on top.
I just hope this works out... Like I said tank has never been looking so good. Just worried about high alk long term?
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