# Dolomite as a source of Ca and Mg



## PlantedRich (Jul 21, 2010)

I guess it is really a basic question but is there something that leads you believe there is not plenty of calcium in the Dallas water? I usually find that when water is drawn from a limestone aquifer, there are plenty of hard water minerals. Many of the folks in the Austin area use water softeners for house use just because there is so much calcium and magnesium. 
Not knowing where your source may be leaves me wondering what caused the worry.


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## niko (Mar 8, 2006)

PlantedRich said:


> I guess it is really a basic question but is there something that leads you believe there is not plenty of calcium in the Dallas water? I usually find that when water is drawn from a limestone aquifer, there are plenty of hard water minerals. Many of the folks in the Austin area use water softeners for house use just because there is so much calcium and magnesium.
> Not knowing where your source may be leaves me wondering what caused the worry.


I didn't look at the tap water and then decide what to do about Calcium and Magnesium. Here's how it went:

*The first time around,* on 2002, I didn't consider the water. I saw a gravel which appearance I liked, put it in the tank, and had my first experience with Dolomite dissolving in water and plants growing like on steroids. Then for 10 years never used it in any way.

*The second time around* I had a tank in which the GH had climbed to 18. I had been using "EI" in the sense most people understand it - add a bunch of fertilizers and change a lot of water every week. Everything is supposed to never accumulate. Yes, things accumulate, and this is what some people are starting to figure out and work on lately. In my case the GH had climbed so high because of my stupidity - I never suspected that a tank chock full of plants would not absorb my pinch of CaCl2 once a week considering I was using 100% RO for water changes. Plants looked fine but not really growing their best - customer tank so if anything was ugly I'd have to change it.

The steps described in the first post in this thread are taken from the experience with that tank. I had to bring the GH down AND adjust the Ca:Mg. But going from GH18 to GH3 with CaCl2 and MgSO4 would be a disaster - adding tons of Cl2 and S. So I used sources tha didn't add them. It is all described above.

How do I know if the Dolomite really made a difference? Well, at first I tried to reduce GH and adjust Ca:Mg with CaCl2 and MgSO4. Plants just would not budge growing. I started to suspect accumulation of "something" - most likely S. So I started to use MgCO3 instead of MgSO4. That lead me to looking for a "clean" source of Mg - one without S. I remembered the Dolomite experience from 10 years ago and gave Dolomite a try. The tank transformed. It had never looked better for many years. Plants grew, some plants that I had not seen in years came back from nowhere.

Was that huge change due to lowering GH only? Or because Dolomite does something a little different? Not sure. So here it is:

*Third time around,* 180 gallon tank. Water changes with 100% RO. Adjusted the GH of 8 to 3. Adjusted the Ca:Mg from about 8:1 to 3:1using only Dolomite and MgCO3, never bothered with CaCl2 and MgSO4. Omg. Same thing - plants exploded. I posted about that in the other thread already. I reduced my DIY LED fixture from 180W to only 25W and the growth slowed but I still get shocking rates at a depth of 24" and only 25W. No other fertilizers, just 1" of AquaSoil with 6 months old root tabs. What I see makes a difference is the CO2 - that tank has been without CO2 now for 8 days. Everything looks absolutely perfect, but the plants grow way slower.

That last one is a story that doesn't make a lot of sense. Be my guest and use 25W of any light over a 2' tall, 6' long tank + add a little CO2, maybe to 6.8. You are not getting anywhere fast. But this tank is. That makes me look for explanations in the microorganism setup of the tank, Dolomite dissolving in some efficient to use way, etc. 

Only way you can know if Dolomite works for you is to give it an honest try. I suggest using good test kits - one of the reasons I had GH18 in the first tank I described were bad test kits.


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## easternlethal (Feb 13, 2016)

niko said:


> To reiterate - this thread is about using alternative, clean, sources of the nutrients that the plants need AND about supplying them in a form that has proven to be very efficient. This thread is not about right vs. wrong.


Can you elaborate a bit more on what you mean by 'clean'? How is Mg in dolomite' cleaner' than Mg in MgSO4?

Or do you mean 'pure' because dolomite does not include SO4? If so I think we'd need to know why SO4 is bad since I understand it has benefits for plants too. 

Or do you mean it's better simply because it's naturally occurring and in that sense Epsom salts would work too?

I think maybe you prefer it because it's pure since I read your post that you are trying to prevent 'accumulation'. But what is so bad about that, given it is also a natural phenomenon? Do you suppose that an EI tank has 'accumulated' more than a natural lake?


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## Hoppy (Dec 24, 2005)

I continue to read the posts on this general subject. My hope is that I will eventually learn something that is helpful to me. Until then I have no idea whether I'm wasting my time (which isn't worth all that much anyway) or if I'm on a path that will lead me somewhere. So, please continue.....


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## Solcielo lawrencia (Dec 30, 2013)

Excess sulfate can interfere with phosphate uptake. According to one crop nutrition expert, the ideal P:S is 1:1. How much sulfur is added with the addition of calcium sulfate, magnesium sulfate, and potassium sulfate?

Ca=15, S=12
Mg=5, S=6.6
K=7.5, S=3
PO4=2.6, P=0.8

P:S= 0.8:21.6 = 1:27

To achieve a 1:1 would require adding more than 21mg/L of P, which is 66mg/L (ppm) of phosphate. Is anyone going to add that much phosphate to achieve a P:S of 1:1?

So if there is an explanation as to why using dolomite improved growth, then it may very well be as niko stated, that it prevents the addition of unnecessary sulfate.


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## niko (Mar 8, 2006)

I said it many times above:

*1.* Calculations, water changes, concentrations mean nothing when your tank is not doing well.

You did everything "right". You followed EI, PPS, ADA, whatever. Plants aren't growing anyway. What is wrong? Many things you don't know about.

One reason could be accumulation. Of something. Could be some minor trace element. Could be S or K or P. Whatever. Change water as much as you can. Do you think you removed all accumulated crap? You have no clue.

Ok. So it makes sense to NOT ADD things if you can avoid adding them. For example we do not want extra S or K or Cl. 

Choose:
CaMg-Carbonate (Dolomite) for Mg instead of MgSO4 which adds S.
CaMg-Carbonate (Dolomite) for Ca instead of CaCl2 which adds Cl.
Calcium Nitrate for Ca instead of CaCl2 which adds Cl. 
Calcium Nitrate for N instead of KNO3 which adds K.
Magnesium Nitrate for Mg instead of MgSO4 which adds S.
Magnesium Nitrate for N instead of KNO3 which adds K.

You get the idea: Dolomite adds Ca, Mg, and Carbonate. Nothing else. You can call it a "clean" source of Ca ang Mg because it does not add anything that secretly accumulates. The Carbonate will show as water hardness and that is easily adjusted through water changes and a very simple test. 

*2.*The SECOND reason I talk about Dolomite is that when it dissolves in the aquarium it is definitely more efficient than adding CaCl2 and MgSO4. The plants respond in a visibly faster and better way. Write a scientific article explaining or denying that - the plants will grow better anyway. 

Do you have to use Dolomite? It's up to you.

Bump:


easternlethal said:


> ... Do you suppose that an EI tank has 'accumulated' more than a natural lake?



Fertilize your tank according to EI. Take a water sample to your water company. They will ask you where did you get that toxic water. It has so much Nitrate and Phosphate that it will be classified as toxic. And it has lots of other fertilizers too - all in concentrations that are very very high. You can not find any natural body of water with such levels of nutrients. But somehow all the plants we grow in our tanks survive in Nature.

If you follow EI you will be changing a lot of water. To avoid accumulation of fertilizers. Good luck. The nice calculation shows that if you change 50% of the water once a week + your plants eat X amount of fertilizers you will always remove all remaining ferts with the water change. That is not so. Some things will gradually accumulate. A nice calculation and graph is not real life.

So it is better to keep things out of the tank. Not to try to take them out once you put them in.


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## niko (Mar 8, 2006)

Hoppy said:


> I continue to read the posts on this general subject. My hope is that I will eventually learn something that is helpful to me. Until then I have no idea whether I'm wasting my time (which isn't worth all that much anyway) or if I'm on a path that will lead me somewhere. So, please continue.....



Get some $4 Dolomite. Follow whatever calculations make sense. Get the Ca:Mg ratio to be 3-4:1. See if your plants are doing better. What do you have to lose?

If I show you growth rate pictures will you be convinced? Or you will tell me that there are a million other explanations why when I added Dolomite my plants started to grow that way? And all along you will assume that I'm telling you the entire truth? This last bit is way more widespread than we think. Beautiful aquascapes we all know have such embarrassing secrets that nobody will even believe the truth. 

So, bottom line - spend $4. Try. See for yourself.

Bump:


Solcielo lawrencia said:


> Excess sulfate can interfere with phosphate uptake. According to one crop nutrition expert, the ideal P:S is 1:1. How much sulfur is added with the addition of calcium sulfate, magnesium sulfate, and potassium sulfate?
> 
> Ca=15, S=12
> Mg=5, S=6.6
> ...


Maybe you can also find some information on how Dolomite dissolves in water and how that can be beneficial to the aquatic plants. I do not know of such an article. But as I said - when I started using Dolomite the plants responded very, very fast. I do not attribute that to S not being accumulated. It certainly seems like a result of the transitional states of the ions.

Get some Dolomite. Put in in a tank with CO2. See the results. You will start to wonder what really is going on.


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## Solcielo lawrencia (Dec 30, 2013)

To test if of the reason is due to carbonates, prior to adding dolomite, dissolve it in vinegar to reduce carbonate into carbon dioxide that will be released into the atmosphere. This would eliminate the effects of carbonate reducing to co2 while in the aquarium. IOW, it eliminates CO2 as the variable as dolomite dissolves as the reason for the improved plant growth.


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## brwaldbaum (Jul 10, 2003)

Solcielo lawrencia said:


> To test if of the reason is due to carbonates, prior to adding dolomite, dissolve it in vinegar to reduce carbonate into carbon dioxide that will be released into the atmosphere. This would eliminate the effects of carbonate reducing to co2 while in the aquarium. IOW, it eliminates CO2 as the variable as dolomite dissolves as the reason for the improved plant growth.


How do you control for the acetate?


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## bluesand (Nov 3, 2014)

Hey niko, is there another way of testing your method without buying those expensive test kit? can i use RO water and add Dolomite alone?


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## easternlethal (Feb 13, 2016)

Solcielo lawrencia said:


> Excess sulfate can interfere with phosphate uptake.



What is your source for this and how much -> 'excess'? And how are sulphates worse than carbonates?

I can find articles that say sulphate reduction plays an important role too.


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## dzega (Apr 22, 2013)

snake oil spotted. All the Ca an Mg in tap water comes from dolomite so you are not adding anything that is not already there.


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## Clinton Parsons (Apr 11, 2016)

I have almost NO gh out of my well. TDS 40, 0kh, 0 GH. I have just been adding baking soda and GLA GH Booster (1 gram and 3.5 grams (maybe 3) per 5 gallons water change IIRC)

So if you wanted to add dolomite to an established tank, how much dolomite would you inject under the aquasoil per unit area sq? I just ordered four ounces of the stuff. It can't hurt anything.

BRWaldBaum, plants and bacteria can use the acetate via the glyoxylate cycle as a source of carbon, so you bring up a great point. 

ADA used to sell Penac P. I think it was just powdered calcium carbonate. I think their contract expired recently and they discontinued it, though.


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## GrampsGrunge (Jun 18, 2012)

dzega said:


> snake oil spotted. All the Ca an Mg in tap water comes from dolomite so you are not adding anything that is not already there.


Unless of course you line in an area that's largely Limestone (CaO3), or in our case were you have virtually no carbonate hardness at all..


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## Seattle_Aquarist (Jun 15, 2008)

GrampsGrunge said:


> Unless of course you line in an area that's largely Limestone (CaO3), or in our case were you have virtually no carbonate hardness at all..


Hi GrampsGrunge,

I am guessing you meant that there would be minimum Magnesium (Mg) in the water? Limestone (aka calcium carbonate) would have a lot of carbonate in the water.


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## PortalMasteryRy (Oct 16, 2012)

I ordered the powder on Amazon to try this out. I am the lucky few who can monitor my Ca,Mg and SO4 levels using a photometer and I'm interested to see how my plants will grow with less sulfate being added. The only reason I back down on dosing Ca and K was because of adding too much sulfate in the water by using K2SO4 and CaSO4. 

Regarding Ca:Mg levels. I've seen good results keeping Mg levels around 15-20 ppm with Ca around 40-60 ppm.


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## GrampsGrunge (Jun 18, 2012)

Seattle_Aquarist said:


> Hi GrampsGrunge,
> 
> I am guessing you meant that there would be minimum Magnesium (Mg) in the water? Limestone (aka calcium carbonate) would have a lot of carbonate in the water.


Well yes, like in Southern England with the chalky soils, it would seem that magnesium would be fairly scant in chalk based soils or ground-water. 

Our local case, is entirely different as we have no hardness at all, either carbonate of general.


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## Clinton Parsons (Apr 11, 2016)

Powder arrived today. How much to add per unit area of substrate?

Not looking to micromanage my gh/kh, just want to add some to buffer (pun intended) any nutrient deficiencies in ca, mg that may or may not ever arise.


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## Seattle_Aquarist (Jun 15, 2008)

Hi Clinton,

I have been dosing dolomite for a little over two weeks as a substitute for the Equilibrium, CaCl2, and MgSO4 I was using in hopes of correcting an issue I have been having with one tank. I started a thread and made the first post this weekend.

Clinton, do you normally dose Equilibrium, Mg, or Ca? If not, then initially I would dose 1/8 teaspoon per 10 gallons which will give you about 4ppm of Ca and 2ppm of Mg. If you do a water change, use the same 1/8 teaspoon per 10 gallons of water changed. That should increase your buffering and provide extra Ca and Mg.


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## Clinton Parsons (Apr 11, 2016)

My wellwater has next to no GH/KH and 40 TDS, so I normally add GLA GH booster and Seachem alkalinity booster. 

I thought it was not very soluble in water and was to be put under the substrate?


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## Seattle_Aquarist (Jun 15, 2008)

Hi Clinton Parsons,

Wow, that is some soft water! If you give me the dosing levels for the GH Booster the alkalinity booster along with your tank size I'll see if I can come up with a more accurate number for you.

Dolomite can be placed into the gravel but it does dissolve in water if the water is acidic and there are free CO2 molecules present. The dolomite will not only provide Ca+2 and Mg+2 (the form of Ca and Mg that plants like) but also bicarbonates. Bicarbonates can provide some of the carbon molecules that plants can utilize in photosynthesis.


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## Clinton Parsons (Apr 11, 2016)

Sure, 2 grams sodium bicarb and three grams GH booster per 5 gallons. That's just what I've been doing, at least. Tank is 90-P, so about 50 gallons. 


Without those my pH when left out overnight aerated is 5.58-6.0, so there must be some tannins leeching in from the hardwood forests. It's so soft I don't use my RO unit, but do filter it through three sediment filters and a carbon filter (AFTER the two whole-house filters.)


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## Seattle_Aquarist (Jun 15, 2008)

Clinton Parsons said:


> Sure, 2 grams sodium bicarb and three grams GH booster per 5 gallons. That's just what I've been doing, at least. Tank is 90-P, so about 50 gallons.
> 
> 
> Without those my pH when left out overnight aerated is 5.58-6.0, so there must be some tannins leeching in from the hardwood forests. It's so soft I don't use my RO unit, but do filter it through three sediment filters and a carbon filter (AFTER the two whole-house filters.)


Hi Clinton Parsons,

Your current dosing levels provide the following (per 5 gallons):
2 grams Sodium Bicarbonate = +4.0 dKH
3 grams GH Booster = 18.3ppm Ca & 2.2ppm Mg

Since maintaining the carbonate level is important for stability I would suggest the following dolomite (CaMg(CO3)2) dosage (per 5 gallons):
1.2 grams Dolomite = +4.0 dKH & 13.8ppm Ca & 8.4ppm Mg

Yes, the Mg level is higher but if you do water changes regularly it should not be an issue. The other choice is to reduce the dolomite (CaMg(CO3)2) and add some calcium carbonate (CaC03) in conjunction with the dolomite (per 5 gallons):

0.5 grams of Dolomite + 0.8 grams of CaCO3 = +3.0 dKH + 27.0ppm Ca + 3.5ppm Mg


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## Clinton Parsons (Apr 11, 2016)

I should probably have mentioned that I am also autodosing 10 mL of a 10% K2CO3 solution daily. 


If don't need the dolomite I guess I can just give it away.


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## Hilde (May 19, 2008)

niko said:


> Dolomite will supply more Ca than Mg.
> To maintain a Ca:Mg ratio of 3-4:1. Adjusting your actual ratio to that 4:1 ratio can not be done with Dolomite alone.
> 
> To adjust the Ca:Mg ratio in a "clean" way, not adding anything extra that will accumulate in the tank we use:
> ...


Is there something else you can use to add magnesium? For I find MgCO3 cost around $20. Where do you buy yours from?


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## PlantedRich (Jul 21, 2010)

Hilde said:


> Is there something else you can use to add magnesium? For I find MgCO3 cost around $20. Where do you buy yours from?


Before spending $20 on chemicals, there might be value in asking some simple questions. Maybe Google dolomite and then open another tab and Google dolomite limestone to compare the two. 

I live in limestone country where the water runs through limestone most of the time. Texas and the central US is often on top of a huge limestone layer. So the thought of adding limestone/dolomite to the water is not in my plans at all. I just avoid using RO water and the dolomite is there. There is no shortage of CA/ MG if we don't fight to keep it out like the OP is doing. 

Life can be difficult if one tries to fight the water by removing the minerals and then adding them back. 

When people keep African cichlids which require hard alkaline water and they are in soft acidic water areas, it is common to use cheap basic items like limestone or coral to boost the hardness. 
Before throwing $20 at what might be snake oil, I would try a trip to the landscape supply for $2 worth of dolomite limestone? 

I have found life and tanks are much easier if I avoid two things. One is snake oil and the other is shooting myself in the foot over highly technical ideas.


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## Hilde (May 19, 2008)

PlantedRich said:


> Before spending $20 on chemicals, there might be value in asking some simple questions. Maybe Google dolomite and then open another tab and Google dolomite limestone to compare the two.
> 
> I have found life and tanks are much easier if I avoid two things. One is snake oil and the other is shooting myself in the foot over highly technical ideas.


Yeh I usually don't do anything to change water parameters but I will have to do so when I start injecting Co2 into my tank. For the water is extremely soft.

Definately not going to spend $20 on 1 fert. Are you saying that dolomite Lime instead of calcium carbonate and dolomite would work? Interesting thought!! Shall research that later. For I have dolomite lime.


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## PlantedRich (Jul 21, 2010)

Hilde said:


> Yeh I usually don't do anything to change water parameters but I will have to do so when I start injecting Co2 into my tank. For the water is extremely soft.
> 
> Definately not going to spend $20 on 1 fert. Are you saying that dolomite Lime instead of calcium carbonate and dolomite would work? Interesting thought!! Shall research that later. For I have dolomite lime.


I'm not at all up on dolomite lime as we never need it to boost the calcium, etc. But I might assume it is just a process form of limestone. Check that before taking it as true! 
What I find works in many tanks for cichlids in places like the East coast is that it is pretty simple to just add rocks, coral or seas shells that are made of the calcium/ mg, etc. that we need in soft water. The slow natural erosion then does what we want and doesn't take forever testing, meaureing, and calculating what and how much. Nature has a way of doing things very slowly and that is part of what I try to do in my tanks. Hold it steady and make adjustments very gradually. 
Remember all the post about which rocks will drive change the water parameters and all the worry about which rocks to use? Yes, simple rocks do change the water if it is soft and acidic so that we need more minerals. So I see no need of really complex moves to adjust the water when we want it less acidic and soft. 
Simple thinking tells me this. If we have soft acidic water and want to keep it that way, don't add soft rocks like limestone but if if want harder water, try adding limestone! Sea shells, coral and a number of other items can be used but limestone is cheap and easy for me. 

This is a local creek. I don't need to add limestone and I sure don't fight to take it out! Dolamite is easy to get in my water.


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