Calcium Reactor vs. Two-part System

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<a href=showthread.php?s=&postid=10312805#post10312805 target=_blank>Originally posted</a> by yossarian
Thanks -

I wasn't going to use the Kalk stirrer/doser for Kalk, but instead to mix and dose other chemicals. such as Kent's Liquid Reactor or A+B two-step -- in place of a CaRx.

Sounds like, just like a CaRx, you are stuck manually figuring out the proper dosage.

By the way, Kent's Liquid Reactor has been pretty good to me so far and appears to have the perfect mix of Calcium / Alk.
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A+B two step is a balanced additive but they can not be mixed together previous to the addition, If you do so the products in the independent bottles will react to each other to form insoluble calcium carbonate which which is not in a usable form to add calcium and alkalinity to your system so the two parts have to be added independently.

Regarding Liquid reactor besed on their specifications it is similar to Purple up in which it contains very finelly ground aragonite sand (Calcium Carbonate). In my opinion, because calcium carbonate does not dissolve into it's constituent elements at the normal PH we keep in our aquariums (8 to 8.4) it is just like adding new sand to your system but again IMO it does not provide the usable calcium and alkalinity bffering required.
Eventually may dissolve some if it reaches parts in your system that have a low PH (like the anoxic areas of a deep sand bed) but the same effect is obtained by the dissolution of the sand itself. In other words I do not think Liquid reactor or Purple up are suitable additives for calcium and alkalinity although they may contain other trace elements that may or may not be beneficial to your system.
Furthermore, when those fine particles suspended in the water column are taken with a test sample using the tritration method like we use for calcium and alkalinity, those particles are dissolved by the addition of the acid tritrant thus giving a false reading which will be higher than the actual level of Calcium or carbonate ions in the water and giving you the impresion that they actually add calcium and/or alkalinity.
Here is an article that review this in more detail:
http://www.advancedaquarist.com/issues/july2002/chem.htm
 
OK - I read the articles, but I find that they don't add up and are internally inconsistent.

1) Let's start with a calcium reactor. The particle size of the media used in reactors is relatively huge. It is somewhat analogous to trying to dissolve a brick of sugar in a sink of water - even though you only need a small portion of dissolved sugar at any given moment. Hence, the big equipement, e.g., CO2, water, etc. This, theoretically, dissolves the calcium into liquid form via, primarily, a lower pH caused by the CO2 (e.g., 7.7 versus 8.3). Yet, this liquid is then supplied to the tank water at a pH of 8.3, which, according to the author, is already supersaturated with calcium.

By the way, it is critical to keep the CO2 out of the tank water, or the tank pH will also decrease. This is one downside of a reactor.

2) Turning to AragaMIGHT. This is calcium in a solid form, but it consists of EXTREMELY tiny particles - a mere 10 microns. This is somewhat analogous to trying to dissolve tiny, invisible pieces of sugar in a sink of water - and only a small amount at a time. If it failed to dissolve, I imagine users would start to see solids building up in dead zones within the tank. But I have never heard of such a thing. The author really has no proof that AragaMIGHT fails to turn into a liquid in the tank (even if it takes 10 minutes).

3) Interestingly, the author says that Kent's Liquid Reactor consists of a slurry of calcium (i.e., solid particles of calcium in a liquid). Of course, the author cites to nothing in support of this claim. I believe that the calcium is already in liquid form, as stated by the manufacture. It is pretty easy to commercially make a batch of low pH water, dissolve calcium in it, then package and ship.

4) The author interestingly ignores A+B, which is also a liquid, not a solid.

5) In any case, the author claims that even though you are getting correct measurements using either AragaMIGHT or Liquid Calcium (or presumable A+B), this is misleading because the pH test lowers the pH to 5, thereby causing the solid to turn to liquid in the test tube, giving you a false result. EVEN if this was true, my electronic pH tool does not consist of a test tube and does not lower the pH to 5 during the test. I wonder why the author failed to mention this basic fact?

6) The author claims that "similar issues may apply to calcium tests where the complexing agents used may promote dissolution of CaCO3." Of course, the author cites to nothing in support of this claim (even though this bald assertion is probably not as ridiculous as trying to trick the reader into thinking electronic pH measurements may be false).

7) OK, let's now return to the Calcium Reactor. The purported liquid output (but do we really know its a liquid or a slurry?) is at 7.7 pH or so. It is then abrupty changed to 8.3 when it hits the tank of supersaturated water. Why then doesn't the Calcium precipiate out of this supersaturated water and turn back into a solid (to the extent it was ever a true liquid to begin with). According the author, the user would never know because his test equipment would then give false readings, just like with the AragaMIGHT and Liquid Reactor. :) This again is basic chemistry. A change of a solid to a liquid can usually be reversed by reversing the procedure (e.g., change of temperature, change of pressure, or, in the case of the author's theory, a change of pH).

8) My guess is that the author has a vested interest in calcium reactors or their media.

9) At the end of the day - I'll just trust my measurements. Liquid Reactor works for me. Ultimate proof is in the healthy livestock.
 
7) OK, let's now return to the Calcium Reactor. The purported liquid output (but do we really know its a liquid or a slurry?) is at 7.7 pH or so. It is then abrupty changed to 8.3 when it hits the tank of supersaturated water. Why then doesn't the Calcium precipiate out of this supersaturated water and turn back into a solid (to the extent it was ever a true liquid to begin with). According the author, the user would never know because his test equipment would then give false readings, just like with the AragaMIGHT and Liquid Reactor. :) This again is basic chemistry. A change of a solid to a liquid can usually be reversed by reversing the procedure (e.g., change of temperature, change of pressure, or, in the case of the author's theory, a change of pH).
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You bring up an excellent question. It kind of reminds me of the old addage of "what goes up must come down".

What is actually keeping the water coming from the reactor saturated to the extent that it remains in the water for the use by our corals?

How does it survive the sudden pH increase once it leaves the reactor?

....both excellent questions that I have seen little discussion on (im sure it out there... I just havent found it).

If our tanks were kept at a pH of 7.5 or so, it would make sense that the CaCO3 would remain in the water column, but if that were the case, we wouldnt need the reactor equipment. We could just dump the media directly into the sump!

Im curious to hear what others have to say/comment on this. Does anyone use a Ca reactor with an electronic Ca test?
 
yossarian:
Because it will take a long post, rather than trying to explain the chemistry of carbonates and why the Calcium and Alkalinity ions dissolved in the reactor effluent do not precipitate and try to describe how the carbonic acid turns into bicarbonate and the bicarbonate into carbonate as the PH changes and how other ions like magnesium can prevent precipitation I would recommend you to research a bit more for a deeper understanding. Here is a good reference were to start.

The thermodynamics of the carbonate system in seawater. Millero, Frank J. Rosenstiel Sch. Mar. Atmos. Sci., Univ. Miami, Miami, FL, USA. Geochim. Cosmochim. Acta (1979), 43(10), 1651-61.

By the way, the author of the article uses Kalk dripping from a reservoir and does not even own a reactor. IMO accusations of a vested interest in calcium reactors or their media are out of line.
 
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jdiek - can you please send me a copy of that article?

I meant no ill will regarding vested interests. I don't know the author of those articles, and don't know whether or not he has a vested interest in equipement. I stand corrected and humbled.
 
LOL!

Leave it to a patent lawyer to make a post like that!
(No offense intended... it was very well thought out, and asked some good questions.)

Yossarian, if you've taken away anything from this thread, it's that all roads lead to Rome. Some are brick, some are sand, some are... well you get the gist.

By way of a correction, the effluent coming out of my reactor is at roughly pH 6.5, far below your measurement of 7.x for the effluent.

It sounds like Kent's Liquid Reactor is a somewhat higher concentration of the effluent that comes out of a reactor, if both the Alk and Ca are being delivered by the same bottle. I'm a total chemistry goober, so I'd just be guessing, but it seems they've found the maximum point at which they can store both Alk and Ca before the two react and precipitate.

So, let's say we take the vendor's claims at face value. The cost of that product is $32 per 64 ounces. Whoa! Depending on your tank demands, you could outpace the cost of a reactor in short order.

Also, you have no control over the specific aspects of the additives. If only your Alk falls low, you can't dose the one, without introducing the other.

At the end of the day, as they used to say in the 1960's, "If it feels good, do it!"
 
<a href=showthread.php?s=&postid=10317117#post10317117 target=_blank>Originally posted</a> by yossarian
jdiek - can you please send me a copy of that article?

I meant no ill will regarding vested interests. I don't know the author of those articles, and don't know whether or not he has a vested interest in equipement. I stand corrected and humbled.
Click to expand...

Do not worry.

There is a sticky of chemistry articles regarding chemistry in the aquarium a lot of them from Rady Holmes and other authors.
Of special interes will be the ones on chemistry in the aquarium, What is Calcium, What is Alkalinity and selecting supplementation methods.
They make for a very interesting and enlightening reading which I fully recommend to anyone interested in marine and reef keeping aquariums.

Here is the link to the articles:
http://reefcentral.com/forums/showthread.php?s=&threadid=102605

Regarding the author's background here a brief bio that I will let talk by itself:

"Randy Holmes-Farley has a BA in chemistry and biology from Cornell University (1982) and a PhD in chemistry from Harvard University (1986). He has 57 patents, numerous publications and several awards in a variety of chemical fields. In 1992 he helped start a pharmaceutical company (GelTex Pharmaceuticals). It was eventually bought by Genzyme where he now has the title of Vice President, Chemical Research. Randy is also the co-inventor of two commercial pharmaceuticals (Renagel and WelChol).

Randy has been keeping reef aquaria for just over 10 years. He has been active on a variety of reef internet forums for that same period, and has been especially involved in chemistry-related discussions. For the past four years he moderated The Reef Chemistry Forum at Reef Central. He has authored many reefkeeping articles with a chemistry emphasis for Fishnet, Aquarium Frontiers, Advanced Aquarists Online Magazine, and Reefkeeping Magazine.

Randy lives in Arlington, Massachusetts (outside of Boston) with his wife Becky and two daughters (ShuLan, 6, and Savannah, 8).
 
"5) In any case, the author claims that even though you are getting correct measurements using either AragaMIGHT or Liquid Calcium (or presumable A+B), this is misleading because the pH test lowers the pH to 5, thereby causing the solid to turn to liquid in the test tube, giving you a false result. EVEN if this was true, my electronic pH tool does not consist of a test tube and does not lower the pH to 5 during the test. I wonder why the author failed to mention this basic fact?"

This stuck out to me.


Testing pH doesnt really tell you anything about Ca or Alk. Well, it tells you something about Alk if you already know the CO2 concentration in your water.
 
Interesting.

By the way, I am still waiting for someone to send me a copy of that article and/or explain why the calcium coming from a calcium reactor at 6-7 pH is "magical" in that it is the only molecule that won't precipitate when it hits the 8 pH supersaturated tank water.

Also, the people with reactors are mistaking themselves in thinking that only the people who dose chemicals are being taken for a high margin profit ride. The markups on reactors are ridiculous. The markups on reactor media are even more ridiculous. And, don't forget the pH controller that most people use with reactors ($200), the CO2 solenoid ($200), the reactor itself ($750+ depending upon size, quality), and repeated media purchases. That money would support chemical dosing for well over 10 years.

I saw that Randy wrote those previous articles, and while his chemical background is impressive, it does not explain what appear to be jury-rigged experiments to achieve a pre-desired, known result. I am probably missing something in the articles, but, to date, no one has told me what it is.
 
<a href=showthread.php?s=&postid=10343287#post10343287 target=_blank>Originally posted</a> by yossarian
Interesting.

By the way, I am still waiting for someone to send me a copy of that article and/or explain why the calcium coming from a calcium reactor at 6-7 pH is "magical" in that it is the only molecule that won't precipitate when it hits the 8 pH supersaturated tank water.

Also, the people with reactors are mistaking themselves in thinking that only the people who dose chemicals are being taken for a high margin profit ride.

I saw that Randy wrote those previous articles, and while his chemical background is impressive, it does not explain what appear to be jury-rigged experiments to achieve a pre-desired, known result. I am probably missing something in the articles, but, to date, no one has told me what it is.
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I can't explain why the Ca from a reactor doesn't precipitate, but I can tell you that it doesn't. Maybe for the same reason that if I dilute salt in a glass of water and pour it into my sump the salt doesn't precipitate out. Nevertheless, the fact remains. Thousands (or millions, perhaps) of reactor users can't be delusional. The effluent just doesn't precipitiate.

Everything in this hobby, unless it's a DIY project, is expensive. If there's a vendor behind it with intent to grow a brand name, then there's a marketing and advertising budget, layers of distiribution partners, a corporate infrastructure with salaries to pay, all causing the product to increase in price. But you'd be mistaken to think that doesn't apply to any industry... computer equipment, automobiles, or anything else.

That's a huge limb you went out on regarding Randy. I don't know the guy personally, and have no stake in his articles, but it wouldn't surprise me if you get jumped on by a bunch of guys here. Seems to me you're the one that's making a wild and unsubstantiated statement about his research based on your pre-desired known result to justify your view about things.

Just my two cents.
 
<a href=showthread.php?s=&postid=10343287#post10343287 target=_blank>Originally posted</a> by yossarian


Also, the people with reactors are mistaking themselves in thinking that only the people who dose chemicals are being taken for a high margin profit ride. The markups on reactors are ridiculous. The markups on reactor media are even more ridiculous. And, don't forget the pH controller that most people use with reactors ($200), the CO2 solenoid ($200), the reactor itself ($750+ depending upon size, quality), and repeated media purchases. That money would support chemical dosing for well over 10 years.
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you are right, it would take an extremely long time to recoup the initial expense of the reactors VS Randy's two part and a doser. I large percentage of users will be out of the hobby before they reach the break even point .

I personally think both methods are great and as far as actual growth/health goes in your tank, there will be little to no difference between the two. In this hobby we often get caught up in the "what is best debate" but the reality is the best and the next best are often indistinguishable as far as real life results are concerned. To decide whats best you need to decide based on other things like ..

Are you a gadget man and enjoy all the stuff required for the reactor? many people simply like more toys and fancy looking items under the tank, many people could care less.

Do you have the money for the initial investment for a reactor ? average investment in a calcium reactor, co2 and media is probably over $1,000. A fully automated 2 part dosing system with media can be $200-500 depending on the quality of doser. Some people simply don't have the extra $500-800 or would rather spend it elsewhere so the choice is simple.

Which one seems less intimidating and easy to set up for your level of skill in the hobby? For the pros on RC setting up and dialing in a CA RX is no big deal and if done right it may ultimately require less ongoing work. For the noobs or even intermediates, Randy's two part is going to much easier and less intimidating because there is no fancy equipment or CO2 canisters and adjusting the amount dosed is as simple as adding or subtracting a few minutes on your digital timer . Your level of skill and choosing equipment you feel comfortable using should play a large roll in your choice.

what are your space requirements ? One of these may fit under your particular tank better than the other .

If even if you thought one of these cal/alk solutions had better results than the other, a combination of the things mentioned above or other variables could easily make the other one a better choice for your needs.
 
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I just have a quick question for those that dose 2 part with a doser. I dose manually and always shake it each day first. how do you keep it from settleing if you use a pump? May be a stupid question but just wondering.
 
My issue is time. The tank must run sometimes for 2-3 weeks with an 8 year old at the helm.

I do not personally care which of a reactor, 2 part, kalk or Liquid Reactor, or any combination of those, is better than one or the other. I just want to know which is better, and why. If I can get it working a reasonable probability of stability for 3 weeks straight, then I'll do it.

But, when someone tells me that the relatively easy liquid dosing that I have been using doesn't work because it changes to a solid as soon as it hits the 8.3 pH supersaturated water -- despite readings to the contrary -- than I simply would like to know why, and why the reactor ouptut doesn't do the same.

So far, no one has been able to explain the reactor side of it. The only reason that I am here is to listen and learn. And, I am not afraid of chemistry - go ahead and lay it on.

At the moment, I am just about convinced to move to an automated, sealed Kalk stirrer-doser (using Kalk) that I think I can get automated and stable for up to 3 weeks. The main problem seems to be that if something goes wrong or needs tinkering, I will not let the 8 year get near the stuff. If I can't get the calcium that I need from it, then I'll cross that bridge at that time.
 
My 2-part doser has been running for the last two weeks, set to dose every hour through my AQ jr. It took me almost no time to set up and takes almost no room in my stand. IMO it is as simple as it gets, I tested the flow rates for a day and then set the pumps to dose my tanks requirement of 120 ml a day by dividng it by 24 and running the pumps for the correct amount of time every hour to dose that amount.

It has been keeping my levels rock solid.

BTW.. I have never needed to agitate my 2-part? I have seen a small amount of precipitate in my large gallon ALK container, but not much at all. Is this really needed as stated above?
 
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<a href=showthread.php?s=&postid=10343696#post10343696 target=_blank>Originally posted</a> by yossarian
I do not personally care which of a reactor, 2 part, kalk or Liquid Reactor, or any combination of those, is better than one or the other. I just want to know which is better, and why.
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Kinda contradicting yourself here, no?
 
<a href=showthread.php?s=&postid=10343287#post10343287 target=_blank>Originally posted</a> by yossarian
Interesting.

By the way, I am still waiting for someone to send me a copy of that article and/or explain why the calcium coming from a calcium reactor at 6-7 pH is "magical" in that it is the only molecule that won't precipitate when it hits the 8 pH supersaturated tank water.
Click to expand...

For the same reason that the calcium and alkalinity already in the tank at 8.0 to 8.2 does not precipitate.
From the article linked below:

Solubility of Calcium Carbonate

In surface seawater, calcium carbonate is supersaturated (although in deep water it is undersaturated for reasons described in this link). That is, there is already more in solution than would form by trying to dissolve solid CaCO3 into the water. It also means that calcium and carbonate are poised to precipitate any time they are given the opportunity (e.g., appropriate seed crystals and a lack of crystallization inhibitors such as magnesium and phosphate).

The equilibrium constant for the dissolution and precipitation of calcium carbonate is shown below:

(3) K = [Ca++][CO3--]

When K exceeds a particular value (the Ksp), the water is supersaturated. If K is less than this value, then the water is undersaturated, and calcium carbonate solid in the water can dissolve. This relationship is normally defined using the supersaturation parameter, which is symbolized as W:

(4) W = [Ca++][CO3--]/Ksp

When W = 1, the solution is exactly saturated. When W exceeds one, it is supersaturated, and when W is less than 1, the solution is undersaturated.

In normal seawater, W ~ 3 for aragonite and W ~ 5 for calcite, though these values have been steadily dropping as carbon dioxide has been added to the atmosphere, reducing the seawater pH. Aragonite and calcite are just different crystal forms of calcium carbonate. Calcite is slightly more stable, and hence is slightly less soluble than aragonite (i.e., has a lower Ksp). Organisms can precipitate both aragonite (pteropods and corals) and calcite (foraminifera and cocoliths), but most of the precipitation in reef tanks is aragonite (although certain organisms such as abalone form both).

Reef tanks often have higher alkalinity and higher calcium than seawater, and hence are more supersaturated than seawater. In tanks with a high pH (such as many tanks using limewater) the supersaturation is also higher than in seawater. At the same alkalinity, if you raise the pH, you convert some of the bicarbonate into carbonate:

(5) HCO3 - + à CO3- - + H+

Within the pH range of most reef tanks (up to about pH 8.5 or so), the amount of carbonate present is approximately linear with the hydrogen ion (H+) concentration because of the relationship seen in equation (5). So if the pH rises from 7.5 to 8.5, there is approximately a ten-fold increase in the carbonate concentration. From pH 8.0 to 8.5, the increase in carbonate is about threefold.

Combining these various factors, here are some combinations of calcium, alkalinity, and pH that have equal supersaturation with respect to aragonite:


W = 1 (risky: dissolution of aragonite begins here)

pH = 7.7
Calcium = 410 ppm
Alkalinity = 2.5 meq/L

pH = 8.2
Calcium = 340 ppm
Alkalinity = 1.0 meq/L


W = 3 (typical of normal seawater)

pH = 8.2
Calcium = 410 ppm
Alkalinity = 2.5 meq/L

pH = 8.0
Calcium = 410 ppm
Alkalinity = 4.0 meq/L

pH = 8.4
Calcium = 260 ppm
Alkalinity = 2.5 meq/L

W = 6 (non-biological precipitation is more likely)

pH = 8.2
Calcium = 410 ppm
Alkalinity = 5.0 meq/L

pH = 8.2
Calcium = 820 ppm
Alkalinity = 2.5 meq/L

pH = 8.0
Calcium = 410 ppm
Alkalinity = 8.0 meq/L

pH = 8.7
Calcium = 410 ppm
Alkalinity = 2.5 meq/L

pH = 8.45
Calcium = 410 ppm
Alkalinity = 4.2 meq/L

How should one think about supersaturation? The higher it is, the more likely it is that precipitation of calcium carbonate will occur. The reason for this is straightforward: if the "pressure" to precipitate calcium carbonate becomes too high, these inhibiting processes will be overwhelmed, and precipitation will take place. As we will see later, there are things that deter the precipitation of calcium carbonate.

If W is reasonably low, some precipitation will take place before the inhibiting mechanisms take control of the crystal surface and prevent further precipitation. This process is what happens in normal seawater. If W is too high, a bigger precipitation event can take place before being halted. In the worst cases, this can lead to a snowstorm of calcium carbonate particulates throughout the tank. Such snowstorms can occur, for example, when too much limewater is added to the tank. In that case, the pH rises and converts much of the bicarbonate to carbonate. W is then driven to unstable levels, and a massive precipitation event takes place.

Calcification by corals is also impacted considerably by the supersaturation of calcium carbonate. As W declines from normal values, calcification by corals becomes slower. Likewise, at higher W, calcification is increased. Many aquarists take advantage of this relationship by boosting W above natural levels. They are thereby able to attain greater growth rates, but run a greater risk of abiotic precipitation of calcium carbonate in the tank than their colleagues maintaining more normal calcium and alkalinity levels.

http://www.reefkeeping.com/issues/2002-04/rhf/feature/index.php
 
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<a href=showthread.php?s=&postid=10343498#post10343498 target=_blank>Originally posted</a> by Snarkys
you are right, it would take an extremely long time to recoup the initial expense of the reactors VS Randy's two part and a doser. I large percentage of users will be out of the hobby before they reach the break even point .

I personally think both methods are great and as far as actual growth/health goes in your tank, there will be little to no difference between the two. In this hobby we often get caught up in the "what is best debate" but the reality is the best and the next best are often indistinguishable as far as real life results are concerned. To decide whats best you need to decide based on other things like ..
Click to expand...

I don't think it could have been said any better!!

I would also like to add that unless you have ungodly and unusual Ca & Alk requirements, lime dissolved in vinegar would most likely suffice... just a thought.
 
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