Two Little Fishies Kalkwasser Reactor

Well, possibly. CC can have a high enough concentration to mag to maintain it, but that's relatively unlikely. It will maintain alk and calcium, though.

 

yes, so far no one has found a method to fully maintain mag with a calcium reactor.

 

This doesn't sound like a very stable environment to me... not saying it wouldn't work, but I don't think it's a long term plan for coral sustainability...

 

Well, they haven't tried using limestone from specific deposits known to contain high magnesium levels.

 

In a nutshell, a kalk rx and calcium rx aim to achieve the same things, but the side effects differ, and folks use these side effects to suit their needs. A calcium reactor will lower the pH, as CO2 causes this phenomenon. A kalk reactor will raise it, as kalkwater has a pH of about 12. Both effluents are rich in both calcium and alk. I don't know about magnesium.

For those (most of us) who battle low pH, a kalk rx helps mitigate the issue and turn the tables in the other direction. Many with normal pH still use a calcium rx, but run it strategically so that the CO2 can offgas before hitting the water column.

Can you run two? Yes, but you had better have some serious calcium load.

As for the comment made earlier--I think you want to avoid precipitation at all costs. Precipitation can leave scale on your glass that might require emptying the tank to solve. I've been there.

 

Well, there is a post around here somewhere about why adding magnesium crystals with very high mag concentrations causes problems for reactors because magnesium dissolves a lot differently than CAC03

 

I pretty much just summarized one of Randy Holmes-Farley's articles.

I do agree that it is borderline of not being stable in aquaria... however that is also why its such a perfect product... you can never go above a dangerous threshold!

If you look at the supernatant reaction, it is more spontaneous at colder temperatures and at lower pH... so with warm water and highish pH its not going to have the least entropy with the ca and carbonate dissolved. Its all just about states and conditions and the transition state of this reaction just so happens to sit right at 8.5 pH in a temp of about 80 degrees. If this happens to your tank it is nothing more than just a phase change for the molecule so it reach equilibrium again.
To an extent, this is also how Ca reactors work: (just with the opposite end of the transition state) it is spontaneous for calcium carbonate to be solid at higher pH obviously, so when you lower the pH of your reaction chamber to 5.5 pH the transition state shifts and the Ca from the coral skeleton dissociates. Apart from lowering pH, the CO2 adds the carbonate to the water so it is in essence the exact same thing, just not empirically proportional like kalk is.

As a side note, when i was dialing in my alk and ca on my new tank with kalk I experienced an overdose and had some precipitate out. I backed off on the kalk and in a matter of hours the tank was once again crystal clear.

now to answer the second part of your question: in excessively large tanks it is not a long term choice for sustaining massive colonies. However, the amount of product (ca and carbonate) entering the tank can be manipulated by a few means: a kalk stirrer to maintain a slurry to keep the reaction farther from equilibrium (decrease in energy of activation through an increase in kinetic energy) or by allowing the reaction to take place in an environment with a lower pH (a little bit of vinegar in RODI is a perfect candidate for this because it releases COOH which is then oxidized by bacteria once in the tank, thus increasing ORP) so more supernatant can be kept in suspension. With these methods it is possible to have a larger sized, kalk only supplemented tank.

-please dont take this as a mean rebuttal, it was simply an in depth explaination to help everyone understand the mechanics of the reaction

 

Not talking about adding mag crystals (Magnesium sulfate or Magnesium chloride), but calcium carbonate (limestone, CC, whatever you want to call it) with a high percentage of "trace" MgCO3 - magnesium carbonate. There's a few limestone deposits that have upwards of 1.5% mag carbonate concentrations.

 

Ok guys thanks for the info.


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I do not own this reactor (yet) but I do have a kalk reactor hooked to me ATO currently and have not had adverse affects that I am aware of. My open-top tank is doing well and my pH stays up around 8.4 which is great on a nano. I do have the ATO return over a powerhead to disperse the slurry as soon as it hits. I plan on doing the same when I get this reactor soon. If you check in a month from now I should have this one going.