Excited for my Bubble Magus Doser!!

[cabrego]

Just a shameless excitement thread! I hope it works well. I will be dosing calcium and Mg with this. My alk is being dosed with my Kalk reactor, any recommendations on what to dose with the third pump? I am thinking either vodka or maybe some kind of trace element..it is out for delivery!

[Chad]

very cool, good for you!! Im looking forward to hearing how that doser works out for you

[zoozilla]

Congratz man. New toys => Much excitement Keep us posted.

[ctenophore]

Just curious, you are dosing alkalinity solution (sodium carbonate or bicarbonate) via your kalk stirrer? Not kalk, right? (which is a balanced Ca/Alk supplement) If the former, that is clever I wonder how you will keep balanced additions of calcium & alkalinity if they are dosed by different systems.

[cabrego]

Just curious, you are dosing alkalinity solution (sodium carbonate or bicarbonate) via your kalk stirrer? Not kalk, right? (which is a balanced Ca/Alk supplement) If the former, that is clever I wonder how you will keep balanced additions of calcium & alkalinity if they are dosed by different systems.

 

I am actually dosing Kalk with my Kalk reactor. My tentative plan is to continue to dose Kalk, and use my doser for calcium, Mg, and one other thing (not sure what it is yet). Of course if I find that the Kalk reactor is sufficiently dosing calcium and alk, I will have an extra dosing pump for something else. I am open to any suggestions as I am new to automated dosing.

 

Based on my previous experience with my kalk reactor I felt that it was not keeping up with my tank's calcium needs- I will be monitoring calcium much closer to understand what my tank's needs really are.

[phisigs79]

why dont you use the third as a topoff through the kalk reactor?

[cabrego]

why dont you use the third as a topoff through the kalk reactor?

 

 

I am already topping off with saturated kalk 24/7 via my float switches. It turns out topping off with 100% saturated kalk is generating to much alkalintiy for my tank so I actually have a line T'd off my kalk RODI feed line and into the sump with a ball valve for control. I also have ball valves on the Kalk output line, this allows me to some what control the mixture of Kalk and RODI that I am topping off with. I know that 100% kalk top off 24/7 is too much because after a couple of days with this method my Alk jumped from about 9 to 11! So I have dialed back the alk and will just continue to tweak until I find a sweet spot.

[ctenophore]

I am already topping off with saturated kalk 24/7 via my float switches. It turns out topping off with 100% saturated kalk is generating to much alkalintiy for my tank so I actually have a line T'd off my kalk RODI feed line and into the sump with a ball valve for control. I also have ball valves on the Kalk output line, this allows me to some what control the mixture of Kalk and RODI that I am topping off with. I know that 100% kalk top off 24/7 is too much because after a couple of days with this method my Alk jumped from about 9 to 11! So I have dialed back the alk and will just continue to tweak until I find a sweet spot.

 

Calcium and alkalinity are added in equal portions by kalk, hence it being called a 'balanced additive'. If your calcium is low, you can just boost it one time via CaCl addition, then let the kalk do the rest. Your tank inhabitants will consume the Ca & Alk in equal portions, they are 'balanced consumers'.

 

If you dose kalk + calcium without alkalinity, you will eventually have a calcium imbalance. If your test kit still says Ca is low, you may have a faulty test kit.

 

I would use one channel for Mg, and the other two for an automated water change system. Balance calcium manually once and you can forget about it if kalk is keeping up with alkalinity demand.

[cabrego]

Calcium and alkalinity are added in equal portions by kalk, hence it being called a 'balanced additive'. If your calcium is low, you can just boost it one time via CaCl addition, then let the kalk do the rest. Your tank inhabitants will consume the Ca & Alk in equal portions, they are 'balanced consumers'.

 

If you dose kalk + calcium without alkalinity, you will eventually have a calcium imbalance. If your test kit still says Ca is low, you may have a faulty test kit.

 

I would use one channel for Mg, and the other two for an automated water change system. Balance calcium manually once and you can forget about it if kalk is keeping up with alkalinity demand.

 

 

Thanks for that piece of information-it is very helpful. In the past everytime my calcium has been on the low side (360 or so) my kalk has been around 7 or so. At the time I was having hardware issues with my Kalk reactor so it was not operating correctly. I have fixed that issue, so hopefully I will be able to better monitor my alk and calcium. I did manually up my calcium and I put my kalk reactor back online. Last time I checked (a few days ago) my alk was at 11 and my calcium was at 420) that is when I dialed back the Kalk output. I will definately do some more tests soon!

[Origami]

Listen to Justin. He's right. You're setting yourself up for a calcium / alkalinity imbalance with the approach that you're suggesting.

 

If your kalkwasser is NOT keeping up with demand (that is, if you find that even with kalk your alkalinity's falling and your calcium is falling over the long term), then by all means, you can use two-part to make up the difference, but you'll need to dose BOTH calcium AND alkalinity (calcium chloride and baking soda) to maintain balance. You can also skip the kalkwasser and do the whole thing with the two solutions, but you may find your pH dropping a couple of tenths or so.

 

If dosing kalk IS keeping up with demand, then you can either stay with that for a while until it can no longer provide for the tank's demands, or you can switch over exclusively to dosing two part. In the former, you'd presumably have two channels of the doser available for other purposes, assuming that the first channel is being used to dose magnesium. Justin suggested using these two channels, if vacant, to do an automated water change. That's a neat idea actually if you have a drain nearby that you can tie into.

 

To go completely to ionic dosing, the three channels are used for calcium, alkalinity, and magnesium.

 

Chemistry Corner

The reason that balance is so important is that the skeletons of our hard corals are made up of (mostly) calcium carbonate. The chemical formula for calcium carbonate is CaCO3. It's made up of one part calcium (Ca) and one part carbonate (one component of what we call carbonate alkalinity, or simply alkalinity). This formula, in gross terms, locks down the ratio of how both calcium and alkalinity is consumed in our tanks. Because we dose to replenish depletion in our tanks due to consumption, it's also the ratio that we use when we dose these components.

 

Kalk is a balanced additive. That is, it provides both calcium and alkalinity in the proper ratios - 1:1. Chemically, it's calcium hydroxide, or Ca(OH)2. For the chemically curious, this is how it breaks down:

 

First, for simplicity's sake, let's break it down into its simple ionic components:

Ca(OH)2 ==> Ca + OH + OH (That's one ion of calcium and two ions of hydroxide.)

 

Now, let's put it in your tank, where it has access to atmospheric carbon dioxide, CO2, that's been absorbed in the water:

==> Ca + OH + CO2 + OH (I've deliberately written it this way to illustrate what happens next.)

 

One hydroxide and the carbon dioxide molecule then combine to form a bicarbonate ion (HCO3). Bicarbonate is the form of alkalinty that our corals consume. So, now we have...

==> Ca + HCO3 + OH

 

When our corals consume the calcium and the bicarbonate, we get...

==> Ca + CO3 + H + OH

 

Which ultimately turns out as:

==> CaCO3 + H2O (In other words, the calcium carbonate of the coral skeleton plus one molecule of water.)

 

Keep in mind that I've purposely simplified the equations shown above for clarity's sake, hiding the second CO2 molecule that enters the picture in the second equation, gets consumed in the 3rd equation, but is returned again in the last. So what's the bottom line?

 

Calcium and alkalinity are consumed in balanced proportions. That's why we dose it that way. Kalk is a balanced additive. The two main two-part solutions, taken individually, are by design imbalanced. You dose them in required proportions to maintain balance. You cannot dose one long term without dosing the other without creating an imbalance (except in specific situations which I won't get into here).

 

Whew. Is it hot in here?

[Origami]

Thanks for that piece of information-it is very helpful. In the past everytime my calcium has been on the low side (360 or so) my kalk has been around 7 or so. At the time I was having hardware issues with my Kalk reactor so it was not operating correctly. I have fixed that issue, so hopefully I will be able to better monitor my alk and calcium. I did manually up my calcium and I put my kalk reactor back online. Last time I checked (a few days ago) my alk was at 11 and my calcium was at 420) that is when I dialed back the Kalk output. I will definately do some more tests soon!

 

Generally speaking, 20 ppm of calcium is consumed for every 2.8 dKH (or 1 meq/l) of alkalinity. Because of the finer resolution of our alkalinity tests, it's often much easier to monitor alkalinity drop and to use the size of that drop to regulate our dosing of both alkalinity and calcium.

 

This ratio is upset slightly by incorporation of magnesium into coral skeletons and export of nitrate through water changes (implying an incomplete nitrogen cycle).

[phisigs79]

thanks Tom thats a good explanation

[cabrego]

Thanks for the info Tom. Has anyone closely studied the role of CO2 conentrations as a function of coral growth rates? I generally try to increase areation to avoid the build up of C02 to minimize PH swings. It look like there is really a balance interms of what is an optimal CO2 concentration in our tank's water. Any insight on that subjet?

[BowieReefer84]

There should be a forum titled "NEXT LEVEL REEFING" with posts like this LOL.

[Origami]

Thanks for the info Tom. Has anyone closely studied the role of CO2 conentrations as a function of coral growth rates? I generally try to increase areation to avoid the build up of C02 to minimize PH swings. It look like there is really a balance interms of what is an optimal CO2 concentration in our tank's water. Any insight on that subjet?

 

Cabrego, if it wasn't you (the original poster), I'd feel bad about hijacking your thread. But since it's your question, let me take a stab at it.

 

First off, I don't know of a study that looks into that. It may be out there, I'm just not aware of it and haven't really looked for it. There ARE studies of the impact of pH on coral growth rates and that is definitely related. Follow along....

 

CO2 is naturally absorbed into our water from the atmosphere. Over the long haul, there's really nothing you can do about it and it's always going to be in the water so long as it's in the air. Nature does the dosing here. Here's the rub, though: Because our homes are so tightly sealed up these days (for energy efficiency), the concentration of CO2 inside of our homes is higher than outside. When CO2 enters the water, it forms carbonic acid which tends to lower the pH of our systems. Because of the higher concentration of CO2 inside of our homes and, consequently, our tanks, our aquariums tend toward a lower pH (that is, they're more acid) than they would be in fresh air. You can easily see the shifting of pH in the diurnal swing of the pH of our tanks. When the tank is brightly lit, our photosynthesizing corals are consuming CO2 in the water column and expelling oxygen as they turn the light energy into chemical energy (sugars) for fuel (much like plants). At night, corals (and plants) respire - that is, they breathe in oxygen and release CO2. The result of this can be seen if we take the pH of our tanks at just before the lights come on (when it is normally low because of all the extra CO2 in the water from respiration) and just after they go off (when, after a day of photosynthesizing, it's high).

 

Our corals rely on a relatively high pH to maintain the potential needed to lay down coral skeleton. Indeed, if the pH dropped too low (below around 7.4 or so), the calcium carbonate of our coral skeletons may actually start to dissolve (albeit slowly at these levels). Not only that, but pH also shifts the ionic balance between carbon dioxide, bicarbonate, and carbonate ions (CO2, HCO3, and CO3) in solution.

 

Another Chemistry Moment...

A few months ago, I read a number of technical journal articles related to CO2 and acidification of the ocean. I also read a couple of other articles by Randy Holmes-Farley and others regarding the relationship between alkalinity and pH. Considering information in each, I produced the following graph relating CO2 concentration and tank pH. I've never released it. This is the first time. Furthermore, this is not to be considered an absolute, immutable relationship. It's a guideline that makes several key assumptions. It's value, however, is clear in that it illustrates the gross relationship between the two and can show you graphically how increased CO2 level can depress your pH and also how alkalinity levels can shift pH.

 

 

The chart relates the level of CO2 in the water column with the pH of the marine aquarium. Various curves are shown. Each curve is for a tank at a specific level of alkalinity. Immediately, what you'll notice about these curves is that they're all shaped similarly indicating a consistent relationship between CO2 levels and pH. What it's telling us is what we, as hobbyists, already have some idea of. That is, as CO2 levels in our tank rises, our tank's pH drops. The curves also tell us that tanks that maintain high alkalinity levels also have a higher pH.

 

The dotted red line that runs vertically about 1/4 of the way into the chart (from the left) is about where the average CO2 concentration is today (as taken from some mountaintop - or likewise remote location - in Hawaii). It's around 378 ppm today. It will be slightly higher in metropolitan areas - closer to 400. To give you some idea of what we have in our homes, CO2 levels of 700 to 800 ppm are not uncommon. Remediation is not normally recommended for levels below 1000 ppm. The difference between 700 ppm and 378 ppm, as you can see from the chart, is around 0.2 pH units.

 

Anyway, I've got the chart posted back in my fish room as a reference. By looking at it and comparing my pH monitor readings and alkalinity tests, I can get some idea of whether or not my tank needs fresh air. (Or, since I draw fresh air, if my alk levels are dropping - which, in turn, is normally an indication that I need to pay more attention to my kalk stirrer.)

[ctenophore]

Very nice explanations, Tom. Is that graph based on your own empirical data or an equation? Can you detail the assumptions made?

 

Also, do you have any equations handy that show the relationship between dissolved CO2 and Ca(OH)₂? As I recall, as OH^- ions increase, CO2 tends toward bicarbonate ion formation. That's where the carbon comes from in the carbonate part of kalk addition. So kalk raises pH (lowers pOH I suppose) and also decreases dissolved CO2 levels.

[ctenophore]

Whoops nevermind, I just saw the CO2 + OH equation above.

[DaveS]

Anyone want to complete this discussion with how Calcium reactors fit into this since many use them in conjunction with Kalk reactors?

[Origami]

Very nice explanations, Tom. Is that graph based on your own empirical data or an equation? Can you detail the assumptions made?

 

It's been a few months, Justin. I'll have to look for some of the papers that I read. One assumption that I recall was that we're considering the solubility of CO2 in "average" saltwater. Saltwater is, as you're aware a very complex solution of many, many ions in many varying concentrations. This alone causes variations. Temperature is another. (Colder water can absorb more gas.) Salinity is yet another. Salinity is assumed to be 35 ppt. I can't recall the temperature assumption, but it's probably around 75 degrees or so (my CRC Handbook is at work and I believe that it's there that I found the dissociation constants for CO2 in salt water).

 

Oh. Here we go. I found some of the papers in the stack next to my desk (what a mess!). They include:

 

Randy Holmes-Farley's paper, "The Relationship Between Alkalinity and pH"

http://www.advancedaquarist.com/issues/may2002/chem.htm

Randy's always a good starting point for this subject in this hobby.

 

I didn't have access to the books that Randy cited in his paper, so I had to pull up what I could using Google:

 

Seawater pH and Anthropogenic Carbon Dioxide by Gerald E. Marsh (found at www.gemarsh.com). A very good article. The appendix was very helpful. (If you read it, equations 1 and A10 have typos: The right hand side of the equations needs to be multiplied by KH.) There's a nice graph on page 4 of the paper that relates partial pressure of CO2 in microatmospheres as a function of pH. In a nutshell, I basically inverted this graph using equations derived from those given in the Appendix after solving for some specific constants using published information about the dissociation of CO2 in seawater.

 

Carbon Dioxide, Dissolved (Ocean) found at

http://www.soest.hawaii.edu/oceanography/faculty/zeebe_files/Publications/ZeebeWolfEnclp07.pdf

 

Rate of Increasing Concentrations of Atmospheric Carbon Dioxide Controlled by Natural Temperature Variations by Dr. Fred Goldberg

 

Anthropogenic carbon and ocean pH by Caldeira & Wickett (Lawrence Livermore National Laboratory) - this was found on the web and was a paper presented at some professional conference.

 

Chapter 8, Reviewing the Impact of increased Atmospheric CO2 on Oceanic pH and the Marine Ecosystem by Turley, Blackford, Widdicombe, Lowe, and Rees (Plymouth Marine Laboratory)

[Origami]

Anyone want to complete this discussion with how Calcium reactors fit into this since many use them in conjunction with Kalk reactors?

 

I'm not sure what you're asking, Dave.

 

Calcium reactors supplement the CO2 in the water column in order to drive the pH down (making it more acid). The calcium carbonate media in the reactor is more soluble in this more acid environment (that is, it starts to dissolve). The consequence is that the effluent has more calcium and carbonate ions, and is a lower pH. This tends to drive the pH of the tank downward as you're basically adding CO2 into your water column through the effluent.

 

In this scenario, though, CO2 is entering the water column via two external entry points(I'm considering respiration as an in-system entry point). They are 1) through atmospheric gas exchange and 2) through the CO2 injection in the calcium reactor. Since, in the long run, we must consider the atmosphere both an infinite source and a sink for CO2 (the prevailing direction of the gas exchange will depend upon the balance between the partial pressures of CO2 in the water and in the air, and the gas solubility), the calcium reactor equipped tank will generally be giving up CO2 to the atmosphere (rather than absorbing it). That's why some people run their calcium reactor effluent into their skimmer intakes - it helps to "off gas" or to "blow off" the excess CO2 from the effluent.

 

People like myself use a calcium reactor while keeping our kalk reactors in operation in order to consume the excess CO2 from the calcium reactor using that second equation listed way back in the "Chemistry Corner" post.

[CHUBAKAH]

Wow, talk about your major hi-jack thread.

 

Just wanted to say that I have been running one of these since they they hit the streets and love it.

[ctenophore]

Wow, talk about your major hi-jack thread.

 

Just wanted to say that I have been running one of these since they they hit the streets and love it.

 

Careful or you might learn something when Tom posts

[Origami]

Wow, talk about your major hi-jack thread.

 

Just wanted to say that I have been running one of these since they they hit the streets and love it.

 

I think that I remember when you got it, too, as you posted about it.

 

I would have felt badly about the hijack except that it was the OP who asked the question that took us down this path. I think that there's good info here. Perhaps it's too bad that it's buried in this thread....

[Origami]

Also, do you have any equations handy that show the relationship between dissolved CO2 and Ca(OH)₂? As I recall, as OH^- ions increase, CO2 tends toward bicarbonate ion formation. That's where the carbon comes from in the carbonate part of kalk addition. So kalk raises pH (lowers pOH I suppose) and also decreases dissolved CO2 levels.

 

You're talking about the carbonate species distribution curve, I think. This one?

 

[ctenophore]

Anyone want to complete this discussion with how Calcium reactors fit into this since many use them in conjunction with Kalk reactors?

 

One nice feature to remember with using both a calcium reactor and kalk reactor simultaneously is not only do they cancel out each others' potentially negative effects (low pH, high pH) as Tom said, but they both provide balanced additives without extra ions. Both only give you calcium and carbonate, not sodium carbonate and calcium chloride like the two-part system does. Normally this isn't a big deal since the buildup of sodium and chloride happen very slowly and are already found in far greater concentrations in seawater than calcium and carbonate. Regular water changes ensure the imbalance never becomes a problem, but if the water changes are too small or infrequent, over time you may see an issue with an ion imbalance, especially in high demand sps systems where a lot of two-part is being added. Hence the development of the Balling method, which to me is clever but complex. I prefer simple chemistry, only dealing with Ca and HCO3.