Water testing

[thdesilva2000]

Hi all, I've never grown Tonina etc, but I probably wouldn't re-mineralise your RO water at all with a known weight of your salt mix.

You can use your tap water to cut the RO with, you are only going to need a very, very small volume of tap, so it doesn't really matter too much about the quality of the tap water. You will only really be adding Ca++ and HCO3- ions, because of the geology (Chalk).

Rather than aiming for a specific dGH/dGH value, you can use a conductivity meter to give you a datum (I'd aim for about 50 - 100 microS), and then use the <"Duckweed Index"> as an indication of when to feed the plants. The conductivity will rise after the fertiliser addition, but will drop back down again as you use RO for the water changes.

If you would rather use the salt mix, you can. Just do the same, add the amount of mix that takes you to ~100 microS in the tank. These are very small additions of salts.

Again it isn't too every-bodies taste, but I would add enough tannins to tint the water. Oak leaves, or Alder cones, are fine for this, and should allow the pH to drop down below pH7.

You will have to balance the amount of floating plant, and the tint, against the light requirements of the Tonina, and a lot of other <"plants aren't going to enjoy themselves">, due to the low nutrients and soft water.

cheers Darrel

Very interesting, for every 1L of RO, how much tap would I need to cut the RO with? A friend from the UK who successfully grows Toninas adviced the following:

“Here’s some info on the mineral I use in ro. I use measuring spoons for the quantities, per 25 litres of ro with 0dgh and 0dkh. 0.5ml of calcium sulphate, 1.25ml of magnesium sulphate and 2ml of potassium carbonate, this should give you roughly 3-4 dgh and 2-3 dkh. This should keep your water soft enough but stable enough for tonina but they are still a tricky plant”.

I am going to use DIY chemicals from Ebay so not aiming to spend a fortune on salts. I spent about £10 on the salts which is going to last two years with 50% weekly water changes.

What are your thoughts? Thanks for the help.


Sent from my iPhone using Tapatalk

 

[dw1305]

Hi all,

“Here’s some info on the mineral I use in ro. I use measuring spoons for the quantities, per 25 litres of ro with 0dgh and 0dkh. 0.5ml of calcium sulphate, 1.25ml of magnesium sulphate and 2ml of potassium carbonate, this should give you roughly 3-4 dgh and 2-3 dkh.

That sounds about right, and if the plants are growing that is a good enough recommendation. I'd make the salt mix up, as mixture in those proportions, and then add a very small amount of it to the water. Go away and wait a bit (for the potassium carbonate to fully disassociate) then measure the conductivity and repeat if necessary.

You are going to be dealing with very small volumes of salts. You also need to take into account the "water of crystallisation", so magnesium sulphate will be MgSO4.7H2O and ~10% Mg, potassium carbonate K2CO3.2H2O and calcium sulphate, the dihydrate etc.

for every 1L of RO, how much tap would I need to cut the RO with?

It will be a very small volume, but most tap water will vary a bit during the year. That is the great joy of the conductivity meter, you dip it in and it gives you a reading. It is a lot easier than mucking about with very small volumes, or weights, of salts.

This should keep your water soft enough but stable enough

You can just ignore pH, your water will never be stable, vegetated soft water never is, either in the tank or in nature.

Because you have very little carbonate buffering, changes in the relative amounts of CO2 (acid from the dissolution of the very small percentage of CO2 that becomes H2CO3 and then H+ & HCO3- in solution) and dissolved oxygen (oxygen is the base in OH-) during photosynthesis will have a large effect on pH.

Acidity and alkalinity, and pH as a measure of them, isn't straight forward. If you have stable pH around pH7 in a planted tank, you don't have soft water.

cheers Darrel

 

[thdesilva2000]

Hi all, That sounds about right, and if the plants are growing that is a good enough recommendation. I'd make the salt mix up, as mixture in those proportions, and then add a very small amount of it to the water. Go away and wait a bit (for the potassium carbonate to fully disassociate) then measure the conductivity and repeat if necessary.

You are going to be dealing with very small volumes of salts. You also need to take into account the "water of crystallisation", so magnesium sulphate will be MgSO4.7H2O and ~10% Mg, potassium carbonate K2CO3.2H2O and calcium sulphate, the dihydrate etc. It will be a very small volume, but most tap water will vary a bit during the year. That is the great joy of the conductivity meter, you dip it in and it gives you a reading. It is a lot easier than mucking about with very small volumes, or weights, of salts.You can just ignore pH, your water will never be stable, vegetated soft water never is, either in the tank or in nature.

Because you have very little carbonate buffering, changes in the relative amounts of CO2 (acid from the dissolution of the very small percentage of CO2 that becomes H2CO3 and then H+ & HCO3- in solution) and dissolved oxygen (oxygen is the base in OH-) during photosynthesis will have a large effect on pH.

Acidity and alkalinity, and pH as a measure of them, isn't straight forward. If you have stable pH around pH7 in a planted tank, you don't have soft water.

cheers Darrel

Thank you Darrell, I tested the water and here are my results.

PH of about 7.8, GH 22 and KH 13

This at the end of the CO2 cycle (pressurised), drop checker is green.

This is a day after making 25% RO water change (no remineralisation), what do you make of this?

Sent from my iPhone using Tapatalk

 

[dw1305]

Hi all,

This at the end of the CO2 cycle (pressurised), drop checker is green.

The pH is because of the CO2 ~ HCO3 equilibrium, at 400ppm CO2 you get a pH of ~pH7.8 when you have carbonate buffering. The drop checker is green because of the additional CO2 you've added, which has diffused across the air gap in the drop checker, into the 4dKH fluid and changed the colour of the bromothymol blue pH indicator, bromothymol blue is a narrow range pH indicator (yellow at pH5 & blue at pH8) with green about pH7. In the test tube the added CO2 will have diffused into the atmosphere and you then record the ambient pH. Adding CO2 doesn't affect the alkalinity, just the pH.

I'm not a CO2 user, you will need to find some-one who has grown Tonina with added CO2 to give you some idea of what fertilisation scheme they used. Because you have higher CO2 (which normally would limit plant growth) and higher light you may need to raise the nutrient levels (and therefore the conductivity) a lot higher.

PH of about 7.8, GH 22 and KH 13

The dKH and the dGH should be much the same, this is because the source of the dGH (multivalent cations) and the dKH (carbonate hardness) is both from dissolved limestone (CaCO3), chalk is really pure CaCO3 (that is why it is so white) and doesn't really contain much else. The derivation of both dGH and dKH is a bit strange, but if you want to know the details it is in <"this thread"> and <"links">.

The KH test kit you have actually measures alkalinity, using a modified acid base titration (you count the number of drops?). The pH indicator is such a wide range (it is a universal indicator) so it doesn't give you much precision, especially around pH7. If you've added 25% RO you have reduced your dKH and dGH by 1/4 (and also your conductivity by 1/4). If your test kits tell you different the problem is with the test kits.

That is why I like conductivity meters, they are robust and accurate over a huge range of water values.

cheers Darrel

 

[thdesilva2000]

Hi all, The pH is because of the CO2 ~ HCO3 equilibrium, at 400ppm CO2 you get a pH of ~pH7.8 when you have carbonate buffering. The drop checker is green because of the additional CO2 you've added, which has diffused across the air gap in the drop checker, into the 4dKH fluid and changed the colour of the bromothymol blue pH indicator, bromothymol blue is a narrow range pH indicator (yellow at pH5 & blue at pH8) with green about pH7. In the test tube the added CO2 will have diffused into the atmosphere and you then record the ambient pH. Adding CO2 doesn't affect the alkalinity, just the pH.

I'm not a CO2 user, you will need to find some-one who has grown Tonina with added CO2 to give you some idea of what fertilisation scheme they used. Because you have higher CO2 (which normally would limit plant growth) and higher light you may need to raise the nutrient levels (and therefore the conductivity) a lot higher. The dKH and the dGH should be much the same, this is because the source of the dGH (multivalent cations) and the dKH (carbonate hardness) is both from dissolved limestone (CaCO3), chalk is really pure CaCO3 (that is why it is so white) and doesn't really contain much else. The derivation of both dGH and dKH is a bit strange, but if you want to know the details it is in <"this thread"> and <"links">.

The KH test kit you have actually measures alkalinity, using a modified acid base titration (you count the number of drops?). The pH indicator is such a wide range (it is a universal indicator) so it doesn't give you much precision, especially around pH7. If you've added 25% RO you have reduced your dKH and dGH by 1/4 (and also your conductivity by 1/4). If your test kits tell you different the problem is with the test kits.

That is why I like conductivity meters, they are robust and accurate over a huge range of water values.

cheers Darrel

Thanks, will look into conductivity meter.

Yes, in this test kit, you measure the drops, NT labs test kit.

I dose 5ML of TNC complete daily (macro and micro all in one mix), my tank is 90L.

Will be putting up my weekly test results here if anyone is interested.

Spot on with your calculations, dgh was about 32 before RO, so roughly 1/4 drop after RO.

Thanks again


Sent from my iPhone using Tapatalk