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Approximating and Maintaining Water Chemistry of a Meromictic Lake

hydrophyte

hydrophyte

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Approximating and Maintaining Water Chemistry of a Meromictic Lake

I'm starting a new project as a continuation of my Stromatolite Reef setup maintained with hypersaline (85ppt) water and 2-part calcium + alkalinity dosing for biologically-mediated precipitation of CaCO3 and stromatolite/microbialite development. This display was designed as a model of Great Salt Lake, Utah environments and was stocked with microbe-bearing substrates from the vicinity of living microbialotes in the lake.

29-VIII-23-Green-Lake-IV.jpg

The next tank I'm planning will attempt to model the fascinating system of Green Lake, New York, a small, but very deep lake near Syracuse, New York. Green Lake is a meromictic lake, with its distinct and permanent water level stratification maintained by its depth, steep sides and the influx of saline water via deep underwater springs.

29-VIII-23-Green-Lake-I.jpg


(Source: Brunskill, G. J. Ludlam, S. D., (1969), FAYETTEVILLE GREEN LAKE, NEW YORK. I. PHYSICAL AND CHEMICAL LIMNOLOGY, Limnology and Oceanography, 14, doi: 10.4319/lo.1969.14.6.0817.)

Among other fascinating features of Green Lake is the thrombolite (a kind of microbialite) reef structure at Dead Man's Point on the lake's eastern shore. I intend to model this an a living aquarium aquascape.

800px-GreenLakesDeadmanPoint.jpg

(Creative Commons image: https://en.wikipedia.org/wiki/Green_Lake_(New_York)#/media/File:GreenLakesDeadmanPoint.jpg)

I'm no chemist, so I could use some help with a starting point for approximating Green Lake's water chemistry, especially the high calcium and bicarbonate concentrations that support the microbial thrombolite development. Here's a table from the Brunskill and Ludlam paper (also shown above) with ion concentrations as measured more than fifty years ago. I'm most interested in conditions at shallower depths and above the level of the chemocline, so see the table below for the values highlighted in yellow. Apparently the lake ecosystem has been maintained in a more or less healthy and stable condition in recent years, so these would not be expected to have changed much in the intervening time.

29-VIII-23-Green-Lake-V.jpg

(Source: Brunskill, G. J. Ludlam, S. D., (1969), FAYETTEVILLE GREEN LAKE, NEW YORK. I. PHYSICAL AND CHEMICAL LIMNOLOGY, Limnology and Oceanography, 14, doi: 10.4319/lo.1969.14.6.0817.)

Green Lake is surprisingly salty for an inland lake. Groundwater flux from the Silurian marine shales, dolomites and other rock layers account for the elevated sulfate, sodium and chloride levels.

Do any readers here have tips or ideas for approximating and maintaining this chemistry? If I can get the organisms to grow, they will deplete calcium and alkalinty, so I also need a plan for replenishment. The aquarium I have in mind is just ten gallons, so a 2-part dosing regime should be acceptable for maintenance. Could an off-the-shelf 2-part be acceptable for the major ions, or will I have to mix up my own salts?

I think that trace mineral concentrations are less critical. I don't intend to dose for those and I should be able to maintain growth of the Cyanobacteria and associated thrombolite organisms with occasional guesstimated dosing of BG-11 or other nutrient medium solution.

Thanks for reading. Like I mentioned I do't have a lot of practice with water chemistry, so any hints, shortcuts or explanations would be greatly appreciated.
 
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Well, sheeeeeeeettttt, this is some hardcore geekery. That's pretty much the only contribution you'll get from me as this is beyond my pay grade, but thought I would let that catch phrase from Isiah Whitlock, Jr. resonate in everybody's head.

Now, place to the more serious posts.
 
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These waters are Sulphate dominated more so than bicarbonate. Doing rough calculations for the significant ions in the water -

1,119ppm SO4
200ppm HCO3
420ppm Ca
72ppm Mg
34ppm Cl
17ppm Na
3ppm K
2.8ppm SiO2
1.8ppm NO3

You’re going to blending a combination of Calcium Sulphate, Magnesium Sulphate, Calcium Carbonate, Magnesium Carbonate, Calcium Chloride, Magnesium Chloride, Sodium Chloride, Sodium Bicarbonate and Potassium Bicarbonate. A careful blend of these compounds will allow you to target the parameters you need, you may not need to use all listed compounds depending on how well you can make the blend fit, I don’t think solubility limits should present a problem making this water. It’s a puzzle for sure but at least you know what the final picture is and what the easiest fit pieces are, the tricky part is scaling them to fit the picture.

🙂
 
X3NiTH said:
These waters are Sulphate dominated more so than bicarbonate. Doing rough calculations for the significant ions in the water -

1,119ppm SO4
200ppm HCO3
420ppm Ca
72ppm Mg
34ppm Cl
17ppm Na
3ppm K
2.8ppm SiO2
1.8ppm NO3

You’re going to blending a combination of Calcium Sulphate, Magnesium Sulphate, Calcium Carbonate, Magnesium Carbonate, Calcium Chloride, Magnesium Chloride, Sodium Chloride, Sodium Bicarbonate and Potassium Bicarbonate. A careful blend of these compounds will allow you to target the parameters you need, you may not need to use all listed compounds depending on how well you can make the blend fit, I don’t think solubility limits should present a problem making this water. It’s a puzzle for sure but at least you know what the final picture is and what the easiest fit pieces are, the tricky part is scaling them to fit the picture.

🙂
Click to expand...

Thanks! Do you think I might be able to figure out a recipe for a rough approximation? I can get economy titrant tests for some of these, but comprehensive laboratory analysis will be way out of budget.

Bookmarking sources for some chemical salts...
 
hydrophyte said:
Bookmarking sources for some chemical salts...
Click to expand...
That is VERY expensive. I am not sure you need reagent grade for what you intend to do. Food grade (which often times can actually be the same purity as reagent grade) would be far cheaper for those compounds available for food use.
I have personally used technical or agricultural grade for all my fertilizers and food grade for my remineralizers and have had no issues with those.
 
Hanuman said:
That is VERY expensive. I am not sure you need reagent grade for what you intend to do. Food grade (which often times can actually be the same purity as reagent grade) would be far cheaper for those compounds available for food use.
I have personally used technical or agricultural grade for all my fertilizers and food grade for my remineralizers and have had no issues with those.
Click to expand...

Yes I'm going to look for the most economical options I can. I want to be able to mix up ingredients and have portions on-hand for 1-gallon or 5-gallon water changes. If I can get the microbes to grow, they will deplete calcium and alkalinity. So I will need some quantity. I just made this list as a starting point for comparison.

If I can get good dissolution in water, gypsum could fulfill a lot of the calcium and sulfate component and it can be very cheap depending on amount and grade...

Calcium Sulfate, Solution Grade GYPSUM 20 lb. -Valufil-650-2
 
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What a nice project !

With the help of @X3NiTH post, I've tried coming up with a dosage of salt for approximating this water chemistry. This is certainly not the most efficient way to do it but here you go :

First of I would dose some reef sea salt for Na and Cl. Plus it would give you a lot of the micro needed some which i don't see where else you could find like strontium (which is found in stromatolites).
For exemple, I did the calculation with 1/630 of the normal dosage of Seachem sea salt.

Then you would need to dose per liter :
3mg KNO3
4,8mg KHCO3
730mg MgSO4.7H20
1260mg CaSO4.1/2H2O
301mg CaCO3
29mg MgCO3
2,8mg SiO2

That would give you approximately this contentration :
3ppm K
1,84ppm NO3
1125ppm SO4
82,5ppm Mg
469ppm Ca
204ppm HCO3
17ppm Na
30,5ppm Cl
2,8ppm SiO2
+some micro

Of course you should verify those dosage before using them,

And all that is just theory.
It doesn't take into account the interaction between all the ions which could lead to some precipitation issue and I haven't looked into the solubility of all those compound.
I just know that SiO2 is hard to dissolve into water and your gonna have to dissolve it into an acid like vinegar.

And i didn't do the math concerning the micro maybe you're gonna need to dose some more.

Now concerning maintaining the concentration of salt :
I really have no idea at which rate the minerals are gonna be depleted but I don't see any other easy way than WC to maintain the water.
It's gonna be really complicated to test regularly and accurately for all the salts and then dose accordingly.
And you could use a TDS meter to know when to change water.

On a sidenote I found some interesting data.
This is the content of microbialite crusts in beachrocks in Kuwait :
https://www.researchgate.net/figure...the-various-types-of-the-crust_tbl2_273916420

Chemical-composition-of-the-various-types-of-the-crust.png
 
It depends on how far you're ready to go. Some compounds may be present in minute amounts but are possibly important/essential for the organisms you're attempting to cultivate. I'd name strontium, barium, flourine, bromine, quite possibly others. Salts of these elements are insignificant in freshwater aquaristics and you'll find them expensive, I'm afraid.
Also, you'll have to keep multiple stock solutions. You can't avoid dosing calcium sulfate which is poorly soluble and tends to create rock precipitates in a stock-solution bottle - Maq's (almost) patented treatment is necessary.
For the macro-elements, it's quite possible to make calculations to use as few compounds as possible.
 
Heelllooo said:
I just know that SiO2 is hard to dissolve into water and your gonna have to dissolve it into an acid like vinegar.
Click to expand...
Not in acids but in strong bases. You may use easily available sodium silicate Na2SiO3 - a liquid glass.
 
Heelllooo said:
What a nice project !

With the help of @X3NiTH post, I've tried coming up with a dosage of salt for approximating this water chemistry. This is certainly not the most efficient way to do it but here you go :

First of I would dose some reef sea salt for Na and Cl. Plus it would give you a lot of the micro needed some which i don't see where else you could find like strontium (which is found in stromatolites).
For exemple, I did the calculation with 1/630 of the normal dosage of Seachem sea salt.

Then you would need to dose per liter :
3mg KNO3
4,8mg KHCO3
730mg MgSO4.7H20
1260mg CaSO4.1/2H2O
301mg CaCO3
29mg MgCO3
2,8mg SiO2

That would give you approximately this contentration :
3ppm K
1,84ppm NO3
1125ppm SO4
82,5ppm Mg
469ppm Ca
204ppm HCO3
17ppm Na
30,5ppm Cl
2,8ppm SiO2
+some micro

Of course you should verify those dosage before using them,

And all that is just theory.
It doesn't take into account the interaction between all the ions which could lead to some precipitation issue and I haven't looked into the solubility of all those compound.
I just know that SiO2 is hard to dissolve into water and your gonna have to dissolve it into an acid like vinegar.

And i didn't do the math concerning the micro maybe you're gonna need to dose some more.

Now concerning maintaining the concentration of salt :
I really have no idea at which rate the minerals are gonna be depleted but I don't see any other easy way than WC to maintain the water.
It's gonna be really complicated to test regularly and accurately for all the salts and then dose accordingly.
And you could use a TDS meter to know when to change water.

On a sidenote I found some interesting data.
This is the content of microbialite crusts in beachrocks in Kuwait :
https://www.researchgate.net/figure...the-various-types-of-the-crust_tbl2_273916420

View attachment 210114
Click to expand...

Thanks very much for performing these calculations! Apologies I should understand this better, but how are the mg/L calculations performed from the ion concentration data?

These are easy to acquire or I have on-hand already:
  • MgSO4
  • CaCO3
  • CaSO4
  • KHCO3
This covers most of the ions, but omits KNO3, SiO2 and MgCO3. I can get magnesium carbonate, although it's rather expensive for the small amount I would use. I thought I had some KNO3 and KH2PO4 (phosphate source?) around here, although I haven't been able to find them yet.

Do you think I really need the heptahydrate MgSO4 and hemihydrate CaSO4? What I have here easy and cheap is regular Epsom salts and gypsum. What's the difference?

Benthic diatoms could be important for Green Lake thrombolite development, so starting with RO/DI water it might be important to make sure the silica component is in there.

A little reef salt sounds like a great idea for sodium, chloride and trace elements.

I have a few other options for trace minerals, including some Guillard's f/2 which I use to grow phytoplankton and also have handy here. This is the basic stock solution recipe for this algae medium...

3i-VIII-23-Green-Lake-I.jpg

(Source: https://ncma.bigelow.org/PDF%20Files/NCMA%20algal%20medium%20f_2.pdf)

...and traces solution...

31-VIII-23-Green-Lake-II.jpg

(Source: https://ncma.bigelow.org/PDF%20Files/NCMA%20algal%20medium%20f_2.pdf)

Vitamins listed in the next table, which I don't include, are thiamine, biotin and cyanocobalamin.

Of course there are also numerous commercial options for reef aquarium traces. Some of these contain strontium, but it is omitted from others...

Trace Elements - Bulk Reef Supply

Your idea of a water change schedule to maintain elements in a range is the best idea. I'm deciding between either a 10-gallon or 21-gallon tank, so I won't have a lot of volume to deal with. These are the two tanks I am trying to decide between...
Here is your per liter suggested dosage again...
  • 3mg KNO3
  • 4.8mg KHCO3
  • 730mg MgSO4.7H20
  • 1260mg CaSO4.1/2H2O
  • 301mg CaCO3
  • 29mg MgCO3
  • 2.8mg SiO2
Summing all those and mixing with water to fill that 21-gallon (79.5 liter) tank makes it just 185 grams (6.5 ounces). Does that sound about right? This concentration shouldn't be expensive or difficult at all for mixing up 1-gallon or 5-gallon water changes.
 
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hydrophyte said:
Apologies I should understand this better, but how are the mg/L calculations performed from the ion concentration data?
Click to expand...
You multiply the concentration in quantity of ion (mmol/L ) by the molar mass of the ion (g/mol = mg/mmol) which give you the concentration in mass (mg/L).
The molar mass tells you the mass in grams of 1 mol of the ion/atom/molecule.
You can easily find online the molar mass of any compound and the percentage of this mass represented by which atom in the compound.
You can ignore the difference between an atom/molecule and the corresponding ion since electron mass is so minuscule.

hydrophyte said:
KH2PO4 (phosphate source?)
Click to expand...
Yes you could dose some, but you will need to dose only 0,3mg per liter to get the concentration in the data.
But maybe it's indispensable to the lifeform you're trying to grow. I really don't know.

hydrophyte said:
Do you think I really need the heptahydrate MgSO4 and hemihydrate CaSO4? What I have here easy and cheap is regular Epsom salts and gypsum. What's the difference?
Click to expand...
The Epsom salt you got is certainly the heptahydrate form. This is the most common you can buy. If it's the anhydrous form or any other one you got it's not a problem, just it will be another dosage.
For Gypsum it's the same it's just another form of CaSO4 and you would needd to use 1490mg per liters.
hydrophyte said:
have a few other options for trace minerals, including some Guillard's f/2
Click to expand...
You have some form of sodium silicate in here which you could use to add the silicate.

hydrophyte said:
Of course there are also numerous commercial options for reef aquarium traces. Some of these contain strontium, but it is omitted from others...
Click to expand...
I wouldn't worry too much about trace as long as you always have a little bit of everything in the water to ensure no shortage of a needed mineral. Like you do for plants. Moreover from the data you posted there seems to be some significative seasonal change in the concentration of the trace element.
But maybe I'm wrong.i'm no biochemist ahah.
You should try to find the maximum of information about the lifeform you will have in the tank to know if there is some toxicity issue with some trace you should avoid

hydrophyte said:
Summing all those and mixing with water to fill that 21-gallon (79.5 liter) tank makes it just 185 grams (6.5 ounces). Does that sound about right? This amount shouldn't be expensive or difficult at all for mixing up 1-gallon or 5-gallon water changes.
Click to expand...
That makes it near 2400mg per liter ( with the little bit of sea salt ) knowing the TDS of the natural water you're trying to replicate is 2000tds and that some of the compound you're gonna dose contain water it should not be too far.

Like I said what I think could be the most problematic is precipitation issue due to the Si.
They even mention it in the trace solution you got.
 
Heelllooo said:
You multiply the concentration in quantity of ion (mmol/L ) by the molar mass of the ion (g/mol = mg/mmol) which give you the concentration in mass (mg/L).
The molar mass tells you the mass in grams of 1 mol of the ion/atom/molecule.
You can easily find online the molar mass of any compound and the percentage of this mass represented by which atom in the compound.
You can ignore the difference between an atom/molecule and the corresponding ion since electron mass is so minuscule.


Yes you could dose some, but you will need to dose only 0,3mg per liter to get the concentration in the data.
But maybe it's indispensable to the lifeform you're trying to grow. I really don't know.


The Epsom salt you got is certainly the heptahydrate form. This is the most common you can buy. If it's the anhydrous form or any other one you got it's not a problem, just it will be another dosage.
For Gypsum it's the same it's just another form of CaSO4 and you would needd to use 1490mg per liters.

You have some form of sodium silicate in here which you could use to add the silicate.


I wouldn't worry too much about trace as long as you always have a little bit of everything in the water to ensure no shortage of a needed mineral. Like you do for plants. Moreover from the data you posted there seems to be some significative seasonal change in the concentration of the trace element.
But maybe I'm wrong.i'm no biochemist ahah.
You should try to find the maximum of information about the lifeform you will have in the tank to know if there is some toxicity issue with some trace you should avoid


That makes it near 2400mg per liter ( with the little bit of sea salt ) knowing the TDS of the natural water you're trying to replicate is 2000tds and that some of the compound you're gonna dose contain water it should not be too far.

Like I said what I think could be the most problematic is precipitation issue due to the Si.
They even mention it in the trace solution you got.
Click to expand...


Thanks very much for these explanations!
 
You can use Calcium Hydroxide to replace any Calcium that is up-taken in the system but personally I wouldn’t be using it to form part of the remineralisation process of RO/DI unless I needed to elevate Calcium levels a little without adding additional Chlorides or Sulphates beyond the target parameters.

Calcium Hydroxide needs twice the amount of CO2 than Calcium Carbonate to form the same amount of Bicarbonate so making up replenishment water using Hydroxides may leave you with solubility and cloudiness issues until it fully solubilises. The overall effect using it would be that it would take much longer for the water to clear if relying on atmospheric CO2 to form the reaction products, obviously using injected pressurised CO2 will speed up the process.

You can read up on remineralisation of desalinated water using Calcium Hydroxide here - https://s3.amazonaws.com/suncam/docs/118.pdf

🙂
 
I've analyzed the numbers provided in post #1, and I'm afraid it'll be quite difficult to make such water. I mean, you can't avoid poorly soluble compounds, like calcium sulfate and bicarbonates. It'll take long time to dissolve. Also, you'll be in trouble when dosing any phosphate - it will precipitate with calcium/magnesium/barium/strontium. These compounds are not totally insoluble (no species is, after all), but to get even minute amounts of phosphate into the water column, you'll have to keep some no small amount of nearly insoluble phosphate(s) present Then, perhaps some bacteria would help to release it.
The list is very likely incomplete. If cyanobacteria are among those you aim to keep, they definitely need cobalt. Cobalt is not on your list.
And, like I said above, some of the elements present in traces may be indispensable for specific life forms - bromine, iodine, barium, strontium, ... definitely silicon and a whole bunch of transition metals - Fe, Mn, Mo, Ni, Co, Zn, Cu, Ti, W, Se ... who knows?
This is not an amateurish undertaking, I'm afraid.
 
X3NiTH said:
You can use Calcium Hydroxide to replace any Calcium that is up-taken in the system but personally I wouldn’t be using it to form part of the remineralisation process of RO/DI unless I needed to elevate Calcium levels a little without adding additional Chlorides or Sulphates beyond the target parameters.

Calcium Hydroxide needs twice the amount of CO2 than Calcium Carbonate to form the same amount of Bicarbonate so making up replenishment water using Hydroxides may leave you with solubility and cloudiness issues until it fully solubilises. The overall effect using it would be that it would take much longer for the water to clear if relying on atmospheric CO2 to form the reaction products, obviously using injected pressurised CO2 will speed up the process.

You can read up on remineralisation of desalinated water using Calcium Hydroxide here - https://s3.amazonaws.com/suncam/docs/118.pdf

🙂
Click to expand...

Thanks very much. So it would basically be the same guidance as for using kalkwasser with a reef tank. I just thought I'd ask though why it hadn't come up. I suppose a kalkwasser setup replacing evaporated water could be integrated for replenishment of calcium, but for for this small setup it makes more sense just to mix up complete re-ionized water for partial and routine water changes.
 
hydrophyte said:
Funny despite my "amateurish" approach
Click to expand...
I didn't mean to hurt you, really. I've just realized that to "copy" the water of given mineral content is quite an advanced job. Fingers crossed! :thumbup:
 
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