Need advice with hard water

Sanniejop

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Oct 6, 2021
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Ok I understand that the hardness of water is important. Ideally it should be 6 or lower(?)

My tap water has an KH of 11. ICP analysis of water supplier tells me it contains Ca 56 ppm, Mg 6 ppm and K 2.6 ppm.

When i want to keep using this tap water as is....
To which ppm values should i dose Mg and K with these Ca and hardness numbers?
I understand that the ratio between those three is important. But is it wise to increase the Mg and K values to meet the ratios with the high Ca or should i keep them lower?

Or is it really worth to invest in RO unit? And all the hassle coming with it.

Thanks in advance,
Sandor
 

Stigigemla

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Jan 30, 2022
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If you add a lot of RO water the hardiness goes down and then the evaporation of CO2 through the surface will go down.
Here in Sweden where I pay 3-4 $ for a pound of CO2 is it profitable. + some plants grows much better in soft water.
 

Lmuhlen

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Jan 20, 2021
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If you add a lot of RO water the hardiness goes down and then the evaporation of CO2 through the surface will go down.

I wasn't aware of this relation between high hardiness (I assume you mean carbonates) and higher CO2 loss.

Could you please explain why that happens?
 

Stigigemla

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Jan 30, 2022
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It is an extremely difficult question to answer in short.
There is an equilibrium between the CO2 in the atmosphere and CO2 in water of about 10 mg/l.
But CO2 in water has an equlibrium with carbonic acid ions (HCO3- and CO3-- ) which is pH dependent. In Tanks with added CO2 we often have much more free CO2 in hard water to get the pH and algae growth down.
I atttach a file here to show impact of pH and kH (alcalinity) on the amount of solved CO2.
The higher the amount of solved CO2 ( and surface agitation) the higher the CO2 loss will be.
It is usual to have a pH of about 7,0 with hardiness 10 wich makes 32 mg/l. For hardiness 2, PH= 6,5 is usual which means 20 mg/l.
We subtract the eqilibrium of 10 mg/l and have 22 or 10 mg/l added. The surface loss of CO2 will be less than half with the soft water.
1643807905580.jpeg
 

Lmuhlen

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Jan 20, 2021
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If I understood your explanation, it seems to me that in the end what you are saying is that having more dissolved CO2 leads to higher CO2 losses, regardless of carbonates. Is there a difference in CO2 loss if I have 30ppm of CO2 and KH2 or if I have 30ppm of CO2 and KH10?
 

Stigigemla

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Jan 30, 2022
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I really don't know but if there is a difference it is probably small or very small.
But in my experience there is great difference in the risk for excessive algae growth with the higher pH.
 

Allwissend

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Equilibrium CO2 is at 3-4 mg L⁻¹ CO2 not 10. You can empirically test this by creating a pure water-bicarbonate solution of KH 4 ( the liquid in your drop checker for example) and test the pH with a good calibrated pH probe. PH will be 7.5-7.6 (indicative of 3-4 mg L⁻¹ CO2) not 7.1.

Unless you are injecting CO2 one should not use these charts to divine a CO2 concentration. When you have lower KH you will achieve a lower pH for the same concentration of CO2. It has nothing to do with evaporation of CO2. You should also know for sure that CO2 (actually H2CO3) is the main source of acidity and bicarbonates are the main source of alkalinity in your aquarium, this is rarely the case so the chart is often prone to exaggerate/overestimate the actual CO2 concentration.
 

Stigigemla

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I believe the chart is used by Dennerle on their homepage to assist when You are dosing CO2.
The number 10 mg/l is for sea water. Sorry I just had it in my head.

@Allwissend I dont understand Your point with this:
"You should also know for sure that CO2 (actually H2CO3) is the main source of acidity and bicarbonates are the main source of alkalinity in your aquarium, this is rarely the case..."
 

Allwissend

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The CO2 concentration in the tables is calculated for bicarbonate solutions where dissolved CO2 is the only source of acidity. Aquarium water has a complex chemistry with many buffers and organic acids lowering the pH. It's not uncommon to read 100 mg L⁻¹ CO2 of the chart (yet fish are fine) because of these errors. Another example would be aquariums using botanicals or peat to lower the pH. Obviously they are not increasing the CO2 concentration.
 

Stigigemla

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I have always considered organic acids as having a very low concentration in planted tanks where we change a lot of water.
I see them most as a theoretical thinking exercise. Or do You have an exampel showing I am wrong? I am interested in thinking exercises.
To add peat in a kH 10 in order to get lower pH would make the water totally black and not very useful for plants. I don't recommend that for beginners.

Maybe we should go back to the OP. What should we recommend Sanniejop.
I recommend an RO to make the water less hard.
What do you recommend?
 

Lmuhlen

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I think there is nothing essentially wrong with his water. He will benefit from dosing nutrients like most people, but I don't think he should worry about reducing concentrations. Maybe some very specific plants that favor soft water will have to be avoided.
 

Sanniejop

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Oct 6, 2021
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My plants are crypto's, anubias, vallisnerias, eichnodorus, hygrophila polysperma, hydrocytile and a tiger lotus.
My main problem is always that my plants are growing pretty well but the old leave are turning ugly pretty soon.
I alway kept NO3 pretty high, above 30ppm, but try to lower it now. So now i dose profito Pottasium seperately and try to feed the fish less. I also dose P and csm half doses according EI.
I did now for two weeks no water changes to see how quick the NO3 would be consumed. It goes not very quick. I also was curious if the KH would drop, but I dont see that happening. The KH seems to be depent of the CO2 dosing rate. Could this be possible because of dissolving snail shells? I have a lot of small snails in my water which seems to become transparent.

I was worried about the abbility of plant to absorb the K with high Ca ppms.
 

Lmuhlen

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It may not be your case, but my experience was that increasing and overall improving CO2 concentration helped with old leaves decay much more than tunning other nutrients.
 
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Sanniejop

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Oct 6, 2021
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It may not be your case, but my experience was that increasing and overall improving CO2 concentration helped with old leaves decay much more than tunning other nutrients.
Ok, i also see that the plants like higher CO2 concentrations. Or the algaes dislike the higher pH? But because of the high KH i need very high CO2 ppm levels to get lime green dropchekers. Poor fish. I watch them closely and it seems when i go to high that they gasp for oxygen at a higher gasps/minute. So i reduced it a little bit.

As i said i am playing with my K levels dosing seperately. With this amount and type of plants, how much usage of K can I expect? On which level should i keep the K. Taking the high Ca in account. Or, as stated above by somebody, does the ratio not matter?
 

Lmuhlen

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You are reading into the pHxKHxCO2 relationship wrong.

What you want is CO2 concentration. The pH drop will be a consequence of that and is of lesser importance. Adding CO2 up to 30ppm requires the same ammount of CO2 with higher or lower KH, and will affect fish respiration the same way in either case.

Dropcheckers measure CO2 concentration (you may argue on its precision and reliability, but it measures concentration). Getting a green dropchecker is a consequence of having a specific concentration of CO2 and doesn't change based on the tank water KH.

I had trouble with fish gasping as well and I still don't really understand what is at play there, but now I have much higher CO2 concentration than I had in the past, and less fish gasping. My KH is on the low side, usually at around 0.5KH. I improved water surface agitation and changed to a CO2 reactor that doesn't fill the tank with bubbles, like my old system did. I suspect that the CO2 bubbles hurt the fish somehow, and that O2 concentrations were low due to bad surface agitation, but I don't see how that would be the case if the plants are pumping O2 into the water.

It may also be that the fish adapted to tolerate more CO2, the same way that humans adapt to higher altitudes after a while and tolerate less O2 concentration.

What I'm trying to say is that gasping fish doesn't imply high CO2 concentration, there can be other reasons.

I don't think you should aim for a pH value based on algae. I'm sure there are algae that like all sorts of water conditions.

Regarding K, I'm not in a position to provide a fine tunning for your dosage, but if you dose at EI levels you are most likely safe. From what I read, proportions are overrated and a healthy excess should conterbalance anything.
 
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Allwissend

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Ok, i also see that the plants like higher CO2 concentrations. Or the algaes dislike the higher pH? But because of the high KH i need very high CO2 ppm levels to get lime green dropchekers. Poor fish. I watch them closely and it seems when i go to high that they gasp for oxygen at a higher gasps/minute. So i reduced it a little bit.

As i said i am playing with my K levels dosing seperately. With this amount and type of plants, how much usage of K can I expect? On which level should i keep the K. Taking the high Ca in account. Or, as stated above by somebody, does the ratio not matter?

Not much K is taken out and fixed by plants but it helps with osmotic pressure and cellular regulation if the concentration in the water is high enough, similar with Ca and many others. 10 mg L⁻¹ K and above is a good starting point for a lot of setups. Plants are adaptable to such a wide variety of (resulting) ratios to the point it doesn't matter.