RO/DI system+agronite=calcium enriched source water

[acrohead500ppm]

I have used this method for 8 yrs in my prop/grow out tanks and it has proved to be cheap and easy and very effiective
Ro/di water has a ph of around 6.3 (spectrapure system)
so i set it up as a 3 ft pvc tube with screaw on endcaps with oles for the ro/di to trickel through this 3 ft pvc pipe filled with agronite
the results were a calciim test of 375 ppm in freshwater!
i use this as my top off water and i have had great results the corals grow fast and the dkh and cal are always TITS

i came up with this idea when looking at prices for a good calcium reactor 500-800 bucks it uses the same method as a calcium reactor does -lowering the ph of the water then inturn dissolves he agronite liberating calcium ions and carbonate

 

[mr.wilson]

I follow the same practice with dolomite and aragonite in the reservoir. Because the flow is very slow, you can use sugar-fine aragonite for quicker dissolution (more surface area), without the fear of dust storms or caking, as experienced with traditional calcium reactors. It acts as a passive calcium, magnesium, and carbonate reactor. It also stabilizes ion-hungry water so plastics aren't attacked and leached into your top-up water.

If you train a few fans at the surface of your display tank, you will have evaporative cooling and a greater amount of remineralized top-up water delivered. A well designed system can have 5 gallons a day of remineralized top-up water, without the headaches of traditional calcium reactors, and the ion antagonism and cost of chemical dosing.

The treated source water is ion-hungry with a TDS of 0 PPM. After a few hours in aragonite & dolomite, the TDS is >250 PPM. It's safe to assume that this 250ppm is the "good stuff" we need to supplement. I use a dual in-line TDS meter to measure treated RO'DI water and the remineralized water exiting the reservoir.

Someone suggested the idea on Wetwebmedia, but it was quickly shot down. They claimed that the media would raise the alkalinity & PH and the process would come to a halt. They neglected to consider that the source water is constantly being replaced by new hungry water for a continuing cycle. Encouraging evaporation further increases efficiency.

If you really wanted to step-up this process, you could use a simple freshwater plant tank-style Co2 reactor, with a Co2 tank and regulator. It doesn't take much carbonic acid to maintain the PH of RO/DI water at 6.5. The gas and media would continue a buffering cycle indefinitely. You may want to consider a second reservoir to buffer the PH up and aerate the water. The second reservoir would have just media with no Co2 dosing.

The practice is very safe, as a measurable amount of elements are added, and only so much can go into solution. If you notice precipitate in your system, you're adding too much. Unlike calcium hydroxide & sodium carbonate DIY mixes, you render an ionically balanced solution without the risk of adding free radicals.

 

[Randy Holmes-Farley]

This is not a very useful method to supplement calcium and alkalinity because almost none of the media will dissolve

Just a tiny bit of CaCO3 dissolves, and the pH rises and no more dissolves. In a reactor, the CO2 keeps the pH down and allows more to dissolve. That does not happen here.

I discuss it here:

Calcium Carbonate as a Supplement
http://www.advancedaquarist.com/issues/july2002/chem.htm

from it (the equations cannot be pasted here) so reading the link may be better):

Dissolution of CaCO3 in Water Prior to Addition

The best way, in my opinion, to use calcium carbonate as a supplement is to dissolve it in fresh water prior to addition. In this sense, it can be used rather like limewater. One can rig up an automatic evaporation replacement system using appropriate pumps and float switches, and just use water saturated with CaCO3 instead of limewater. Alternatively, one can simply pour the saturated water into the tank each day. Unfortunately, the fact that you can add it this way is a mixed blessing. One reason that you can add it this way is that there is so little present that the carbonate does not drive up the pH too much.

So how much goes into solution? This question is rarely addressed directly, and it is because of one big complication: carbon dioxide from the atmosphere. In the case of limewater, it is partially destroyed by atmospheric carbon dioxide (producing insoluble CaCO3 from the dissolved calcium and hydroxide). In the case of calcium carbonate, however, the solubility is actually increased by mixing with carbon dioxide. The reason that the solubility is increased is that the carbon dioxide enters the water, becomes carbonic acid (equation 1), and largely combines with carbonate ions to form two bicarbonate ions (equation 2):

1.
2.

The net effect is that the concentration of carbonate ions declines: since the solubility of calcium carbonate is governed by the multiplication product of the calcium and carbonate concentrations (equation 3), more calcium carbonate can dissolve to regain saturation.

3.

Knowing the Ksp and some other constants, it is a textbook calculation to determine how much calcium carbonate can dissolve in pure water in the absence of atmospheric carbon dioxide. Pankow (Aquatic Chemistry Concepts; 1991) carries out this calculation for calcite (a slightly less soluble form of calcium carbonate than aragonite).

For those really interested in the chemical details, this calculation is actually much more complicated than it would first appear (i.e., more complicated than for a simple salt like NaCl). You cannot simply solve equation 3 for [Ca++] and [CO3--]. You need to take into account the fact that some of the carbonate that comes from dissolution will be converted into bicarbonate (HCO3-) and even carbonic acid (H2CO3). This conversion permits more CaCO3 to dissolve before the carbonate concentration rises too high to dissolve any more. One also needs to take into account the fact that calcium can exist as CaOH+, which effectively lowers the calcium concentration (though not very extensively at pH values below 11).

From this calculation, we find that the solution at equilibrium contains about 6 ppm calcium and 0.3 meq/L alkalinity, and results in a pH of 10.0. If we correct this result for aragonite instead of calcite (which is slightly more soluble), we get about 10 ppm calcium and 0.5 meq/L alkalinity, with a pH of just over 10 (which is what about what I got when I initially dissolved both AragaMIGHT and Southdown aragonite sand in RO/DI water). For comparison, full strength limewater contains about 820 ppm calcium and 41 meq/L alkalinity.

The calculation is even more involved when atmospheric carbon dioxide is allowed to enter the system. Thankfully, Pankow has again done the calculations for us. In equilibrium with normal atmospheric carbon dioxide, the solubility is increased by about a factor of 3, with the alkalinity about 1 meq/L and the calcium about 20 ppm. In this case, the pH drops to about 8.3 as the carbon dioxide enters the system. Confirming Pankow’s calculation, this result is about what I got when I let both AragaMIGHT and Southdown aragonite sand sit in RO/DI water for a few days). Still, these calcium and alkalinity values are about 40X lower than for saturated limewater, so are likely not enough to satisfy the needs of most reef tanks.

At one point I had the bright idea of adding aragonite to seltzer (soda water) bought at the grocery store to really boost the solubility and maybe have a nice, liquid additive. Seltzer has far more carbon dioxide in it than water in contact with normal air (which is why it goes flat when open), and that extra carbon dioxide will cause a great deal more calcium carbonate to dissolve (at 3.5 atmospheres CO2, the solution would contain more than 10 meq/L alkalinity and would be similar to limewater in potency, but much lower in pH). If only I had been able to mix them…… Instead, it ended up a science experiment for the kids, with the added aragonite sand providing a perfect surface for the carbon dioxide to turn into the gas phase and erupt from the bottle as a fountain of water, gas, and sand!

 

[Boomer]

have 5 gallons a day of.....and 25O ppm TDS

If we assume that all of that 250 ppm is CaCO3 in solution, which it won't be, that is 250 x .4 or 100ppm Ca++. for that 5 gals in a net 100 gal. That is a dilution factor of 20:1, which equals a 5 ppm Ca++ increase in the tank system being added in 1 day with a 5 gal evap rate. In reality it would be more like 2-3 ppm Ca++ / day which is about nil. And if the evap rate is lower the increase will be even less

Unlike calcium hydroxide & sodium carbonate DIY mixes, you render an ionically balanced solution without the risk of adding free radicals.

What do you mean not balanced. Calcium hydroxide is a perfectly balanced sup. It is the only substance that adds nothing to the water in an unbalanced form other than some nil tace elements. Even reactor media, Aragonite, Dolomite add unwanted ions. And it is the accumualtion of unwanted ions that makes a system unbalanced.

Ca(OH)2 ==> Ca++ + 2 OH

2 OH + CO2 = 2 HCO3- (akalinity)

and what free radicals are you taking about being added ?

plastics aren't attacked and leached into your top-up water.

That depends on the plastic many are inert to RO/DI water.

If you really wanted to step-up this process, you could use a simple freshwater plant tank-style Co2 reactor, with a Co2 tank and regulator. It doesn't take much carbonic acid to maintain the PH of RO/DI water at 6.5. The gas and media would continue a buffering cycle indefinitely. You may want to consider a second reservoir to buffer the PH up and aerate the water. The second reservoir would have just media with no Co2 dosing.

Then you may as well by a reactor and do it right.

Ro/di water has a ph of around 6.3

You can not measure the pH of RO/DI water, those are false pH readings. There are no ions in the water for the probe to ref to or a test kit to pick up on. Once RO/DI waer has picked up enough CO2 from the air it is another issue. If on the other hand, the RO/DI is kept in sealed container you can not measure its pH.

 

[mr.wilson]

<a href=showthread.php?s=&postid=8761884#post8761884 target=_blank>Originally posted</a> by Boomer

If we assume that all of that 250 ppm is CaCO3 in solution, which it won't be, that is 250 x .4 or 100ppm Ca++. for that 5 gals in a net 100 gal. That is a dilution factor of 20:1, which equals a 5 ppm Ca++ increase in the tank system being added in 1 day with a 5 gal evap rate. In reality it would be more like 2-3 ppm Ca++ / day which is about nil. And if the evap rate is lower the increase will be even less

The actual calcium level in the remineralized water is 40ppm and 2.5 meq/l. Depending on the type of corals you're growing, and the biological processes taking place, this may or may not be enough to replace depleted calcium and other respective elements. The dissolution rate in the passive calcium reactor is about the same or greater than that experienced in the conventional calcium reactor on the system. It can be stepped-up if you require more replenishment.

In my case, I use the passive reactor and a conventional calcium reactor with dolomite and aragonite media. One benefit of the passive reactor is that it can operate with finer media as clogging isn't an issue.

What do you mean not balanced. Calcium hydroxide is a perfectly balanced sup. It is the only substance that adds nothing to the water in an unbalanced form other than some nil tace elements. Even reactor media, Aragonite, Dolomite add unwanted ions. And it is the accumualtion of unwanted ions that makes a system unbalanced.

Ca(OH)2 ==> Ca++ + 2 OH

2 OH + CO2 = 2 HCO3- (akalinity)

and what free radicals are you taking about being added ?

While hydroxide, chloride, sulphate, carbonate, and bicarbonate anions aren't exotic, there is a limit to the number of them that can be added without adversely effecting water chemistry. The practice of dissolving calcium carbonate media allows for the release of proportionate amounts of each desired element bound within it. Chemical dosing is more likely to cause precipitate through poorly prepared stock solutions, overdosing, and impatient dosing practices. Another issue is the grade of chemicals used, as hobbyists have limited access to lab or even food grade chemicals.

Some of these chemicals classify (aggregate) in the storage containers and desiccants can be altered in a humid environment.

That depends on the plastic many are inert to RO/DI water.

There are no truly inert plastics, and PVC is one of the worst offenders, with polypropylene and nylon being less toxic. http://www.ecologycenter.org/iptf/toxicity/index.html

The other issue is gas exchange of deionized water.

Then you may as well by a reactor and do it right.

I use conventional calcium reactors in conjunction with passive reactors. If at some point in time, I can substantiate the merit of passive reactors, and step-up the design to make them more effective, I'll discontinue the use of in-line, in situ reactors.

The benefit of losing a conventional reactor is cost, clutter, fewer pumps, and one less thing to adjust or worry about leaking, breaking, or clogging.

You can not measure the pH of RO/DI water, those are false pH readings. There are no ions in the water for the probe to ref to or a test kit to pick up on. Once RO/DI waer has picked up enough CO2 from the air it is another issue. If on the other hand, the RO/DI is kept in sealed container you can not measure its pH. [/B]

I agree. The PH is neutral at 7.

 

[mr.wilson]

<a href=showthread.php?s=&postid=8760308#post8760308 target=_blank>Originally posted</a> by Randy Holmes-Farley

The best way, in my opinion, to use calcium carbonate as a supplement is to dissolve it in fresh water prior to addition. In this sense, it can be used rather like limewater. One can rig up an automatic evaporation replacement system using appropriate pumps and float switches, and just use water saturated with CaCO3 instead of limewater. Alternatively, one can simply pour the saturated water into the tank each day. Unfortunately, the fact that you can add it this way is a mixed blessing. One reason that you can add it this way is that there is so little present that the carbonate does not drive up the pH too much.

I've used this method in the past with Caribbsea "Aragomight" and Kent "Liquid Reactor". I preferred the Kent product as it dissolves better so it's easier to keep track of how much you've added. I was using a calcium reactor in both instances, so I cannot qualify the extent of their value.

The calculation is even more involved when atmospheric carbon dioxide is allowed to enter the system. Thankfully, Pankow has again done the calculations for us. In equilibrium with normal atmospheric carbon dioxide, the solubility is increased by about a factor of 3, with the alkalinity about 1 meq/L and the calcium about 20 ppm. In this case, the pH drops to about 8.3 as the carbon dioxide enters the system. Confirming Pankow’s calculation, this result is about what I got when I let both AragaMIGHT and Southdown aragonite sand sit in RO/DI water for a few days). Still, these calcium and alkalinity values are about 40X lower than for saturated limewater, so are likely not enough to satisfy the needs of most reef tanks.

These numbers are more or less what I've experienced. When I find the time to experiment with other methods of dissolution, I'll pass on my results, good or bad. Disproving it is as important as proving it, just not as rewarding.

I think the key issue here, is that we're all looking for a better way of supplementing depleted elements. Eric Borneman, for example, has discontinued the use of calcium reactors on his tanks, as he still needs to dose calcium daily to keep it up...and aren't we all looking for a better way to get it up?

 

[Randy Holmes-Farley]

I think that folks just need to recognize that while a small amount of calcium and alkalinity will dissolve into fresh water from calcium carbonate, it is quite small, and is not likely to be enough for most reef systems. It is about 5-10 fold less than calcium hydroxide dissolves, and even that is not enough for many heavy demand systems.

FWIW, I do not see any reason to think calcium hydroxide is less pure than calcium carbonate. it is, after all, just calcium carbonate that has been heated to drive off CO2.

I also do not see any reason to think that quality two part additives or limewater are not ionically well balanced.

 

[Boomer]

The actual calcium level in the remineralized water is 40ppm and 2.5 meq/l. Depending on the type of corals you're growing, and the biological processes taking place, this may or may not be enough to replace depleted calcium and other respective elements. The dissolution rate in the passive calcium reactor is about the same or greater than that experienced in the conventional calcium reactor on the system.

40 ppm Ca++ in make-up water is about nil. You are adding 40 ppm in 5 gal over a 24 hr to 100 gals of water. You are not looking at dilution factors. The dissolution rate and feed rate of a passive reactor is not even close to a calcium reactor in keeping up Ca++ demands.

Another issue is the grade of chemicals used, as hobbyists have limited access to lab or even food grade chemicals.


Have you ever looked at an assay on say Dolomite. You are not adding DOLOMITE a more or less pure mineral to a reactor, it is Dolomite the rock. Most Dolomite is altered Limestone. Dolomite the rock, just contains high amounts of Dolomite the mineral. Such rocks can and often do contain unwanted elements, if we want to use your unbalanced scheme.


While hydroxide, chloride, sulfate, carbonate, and bicarbonate anions aren't exotic, there is a limit to the number of them that can be added without adversely effecting water chemistry. The practice of dissolving calcium carbonate media ,

The issue was Calcium hydroxide. As far as limits go even calcium carbonate has it limits then. They are adding carbonate and bicarbonate ions. The limit is the same. So, your scheme above only pertains to sup's that use chloride or sulfates. You forgot Na+ Normal water changes will bring any of those off-sets back into balance.

At what levels are you saying Chloride, which is already at 19,000 ppm, Sulfate at 2700 ppm and Sodium at 11,000 ppm, is adversely affecting water chemistry ? In the Red Sea and its vibrant coral reefs, they are much higher than that.


You are stretching it on plastics


The benefit of losing a conventional reactor is cost, clutter, fewer pumps, and one less thing to adjust or worry about leaking, breaking, or clogging

I can not disagree on that.

I think the key issue here, is that we're all looking for a better way of supplementing depleted elements

I agree here also but see little benefit from a passive reactor in most cases, when it is only increases the Ca++ 2 ppm or so in a system.

 

[mr.wilson]

<a href=showthread.php?s=&postid=8764688#post8764688 target=_blank>Originally posted</a> by Boomer

40 ppm Ca++ in make-up water is about nil. You are adding 40 ppm in 5 gal over a 24 hr to 100 gals of water. You are not looking at dilution factors. The dissolution rate and feed rate of a passive reactor is not even close to a calcium reactor in keeping up Ca++ demands.

The person who started this thread claims to have 375 ppm in his remineralized RO/DI water. As a result, he feels no need for other methods of supplementation. My claim was less optimistic, and I use calcium reactors on all of my tanks.

According to my crude calculations, that 40 ppm Ca in 5 gallons of water is 2 ppm to the 100 gallon total volume. If I start with a calcium level of 400 ppm, and supplement nothing, my calcium level would take a few days to drop to 398 ppm. I'll check this by turning off my calcium reactor for a week to see how much calcium carbonate it dissolves.

Regardless of its' merit in replenishing depleted elements, I hold value in the ability to stabilize ion-hungry water. From your enthusiasm, it appears that you may use chemical dosing exclusively. As a result, your stock solution will achieve this same stability.

Have you ever looked at an assay on say Dolomite. You are not adding DOLOMITE a more or less pure mineral to a reactor, it is Dolomite the rock. Most Dolomite is altered Limestone. Dolomite the rock, just contains high amounts of Dolomite the mineral. Such rocks can and often do contain unwanted elements, if we want to use your unbalanced scheme.

I use the best quality constituents that are available, but I live in the real world and I'm willing to make some concessions. If I lived in a bubble, I wouldn't be able to import anything into the tank.

The issue was Calcium hydroxide. As far as limits go even calcium carbonate has it limits then. They are adding carbonate and bicarbonate ions. The limit is the same. So, your scheme above only pertains to sup's that use chloride or sulfates. You forgot Na+ Normal water changes will bring any of those off-sets back into balance.

At what levels are you saying Chloride, which is already at 19,000 ppm, Sulfate at 2700 ppm and Sodium at 11,000 ppm, is adversely affecting water chemistry ? In the Red Sea and its vibrant coral reefs, they are much higher than that.

I'm sure you have sound chemical dosing practices, but you are the exception, not the rule. A combination of witchcraft and alchemy are more common as hobbyists are sold everything under the sun at their LFS.

You are stretching it on plastics

I have no choice but to use plastics, but I'm not going to turn a blind eye to their toxicity. As they coat with bacterial film and calcium, they become completely "safe". I'm sure the same people that compile the data on the dangers of plastics, eventually graduate, decide they want a BMW and get a job working for the companies that make the plastics that they wrote their doctorate on. I'm complacent, but I still reach past the plastic cups for a glass.

I can not disagree on that.

I knew if I made my post long enough we'd have to agree on something. Perhaps calcium reactors will go the way of UG filters and wet/dry systems. Time will tell. I don't have any tanks with very heavy coral populations, so calcium reactors work with very little cost or maintenance. If chemical dosing was an option for my clients, I'd discontinue their use in a heart beat.

I agree here also but see little benefit from a passive reactor in most cases, when it is only increases the Ca++ 2 ppm or so in a system.

Agreeing on what doesn't work will get us there a lot quicker.

 

[Boomer]

375 ppm in his remineralized RO/DI water

You can not dissolve that much CaCO3 in a FW solution. = 375 ppm Ca++. Im sure his 375 is ppm TDS as CaCO3, which is x .40 = 150 ppm Ca++ and not 375 Ca++. You have to remove the MW of the CO3--. CaCO3 = 100 MW and the MW of Ca ++ is 40 or 40 %, thus .40 x 375 = 150 ppm Ca++. And all that TDS will not be only Ca++ and CO3--only but by far most will be.

A Calcium reactor delivers allot more that 2 ppm /day. If it did not, a reef tank with a good supply of just coralline algae would never keep the Ca++ levels up to snuff. Do a search on Ca++ daily needs in a avg reef tank.

that 40 ppm Ca in 5 gallons of water is 2 ppm to the 100 gallon total volume

That is correct. Pretend the tank water = 400 ppm Ca++. Remove 5 gals and replace with 5 gal of 440 ppm C a++. The same thing. The Ca++ will only rise about 2 ppm Ca++ in 100 net gals. It can't go higher by magic It is not uncommon to have the Ca++ drop 5-10 ppm in 1 day.



I'd discontinue their use in a heart beat

We can agree on that.

Agreeing on what doesn't work will get us there a lot quicker.


Yes for sure It would be nice for things to be much simpler. I look at some systems and there is so much equipment it is scarier that rendering safe a bomb :lol:

I don't' run tanks anymore, + 30 years was long enough. I just try to help