Remineralising RO

[Skatersav]

Seachem does a mix that looks relatively similar to James' Planted Tank mix... in principle at least: ie no sodium, low chloride. I am going to give that a go because my wife is getting a bit freaked out about how one of our cupboards is looking more and more like a chemistry lab...

Sav

 

[Radik]

I just measured my RO after re mineralization and PH was around 10. Thanks to Calcium Sulphate. Now I am not sure how shrimp safe this would be during water changes I know PH shock is a myth but going from PH 6 to PH 10 in water change seems a lot to me. Any advice on substitute for Gypsum and in what amount for 25L as for Jame's recipe?

I am not using chloride only MgSo4 K2Co3 and CaSo4

 

[dw1305]

Hi all,
Radik don't worry, the calcium sulphate (CaSO4.2H2O) shouldn't change the pH at all, it is the potassium carbonate (K2CO3) that does. It is because you have no H+ ions in the RO, meaning that the there is no reserve of acid and any small addition in alkaline ions will make the pH rise to a high level. Just ignore the pH, honestly it is almost meaningless in unbuffered water.

Using "James' Planted Tank":

1.2g K2CO3 in 25 litres of water = 2 dKH

cheers Darrel

 

[Radik]

Oh ok thanks Darrel, I turned only slightly Co2 and PH is going down quickly while drop checker is dark blue so yes you are right I am just bad in chemistry so glad to have you around

I did test with CaSO4 + MgSO4 without K2CO3 and it increased PH so maybe my gypsum is crap? I am using digital PH meter with electrode not test kits.

 

[Radik]

Oh just realized... I am going to add CaSO4 to Tap water not RO water to see "PH change" as tap water is already buffered.

 

[hotweldfire]

Guys, I've been adding K2CO3 for the last few weeks to my nano and can't get the KH to read 2 or above. I'm throwing in up to 1.5g of it at a time into a 27l P@H cube that gets pure RO for water changes (max 10% a week). Testing either half an hour or 24 hours later shows at most a change of around 0.5 KH, usually no change. So,

- either James calculations are off (unlikely)
- my test kit is a nonsense (likely)
- something is eating up the K2CO3 damn fast

Are KH test kits able to detect this level of change? Are they relatively reliable?

 

[Radik]

Yes depends what substrate you have acids can reduce your KH usually some acids in substrate or water column. KH of 2 has little buffering capacity so it will crash but no worries. Now Darrel would explain it more technically what is happening. Also KH test kits are crap you need really good one. For me API is showing +1 or +2 higher than it really is. Nutrafin KH was sort of OK but there are more precise available.

 

[dw1305]

Hi all,
I think this could be a "real" reading and that Radik is right, the fall of in the dKH it is probably to do with the lyotropic series and the exchange of cations (and anions):

Monovalent ions (like K+) will also replace H+ ions, but they don't add any dGH. This is actually a 2 way process and those ions can be replaced by H+ ions etc and become available to the plant as the concentration of the ions change around the negatively - charged exchange sites of the clay mineral. This is the "LYOTROPIC SERIES":
most tightly bound H+ = Al3+ > Ca2+ > Mg2+ > K+ = NH4+ > Na+ least tightly bound. Adding large amounts of one cation will replace others, regardless of their position in the lyotropic series. For example Na+ could replace Ca2+ on the mineral's exchange sites if sufficient concentration of Na+ existed in tank water.

You need to measure the conductivity before and after the addition of the potassium carbonate (K2CO3), if the K+ ions (which will contribute to conductivity) are being exchanged for H+ ions (which don't) the conductivity should rise initially and then fall as the K+ ions are exchanged for H+ ions.

cheers Darrel

 

[hotweldfire]

What sort of time frame for the rise and fall Darrel?

 

[dw1305]

Hi all,

What sort of time frame for the rise and fall Darrel?

I'm not entirely sure, but a few readings over 24 hours should give an idea. All the K+ ions will be in solution, again I'm not sure about the bicarbonate ions, the amount of these will depend upon the carbonate/carbonic acid equilibrium. Assuming the cation exchange sites on the clays are still largely filled with H+ ions you should get an initial linear fall in conductivity as K+ ions replace H+ ions on the clays, and H+ ions replace K+ ions in solution. I think this decline in conductivity will slow down as the conc. gradient between the substrate and water lessens.

Cheers Darrel

 

[David Shanahan]

I'm a bit confused.

You go to you local fish shop, buy some RO water from them, then add your Macro and Micro nutrients. So will these buffer the water (with a little bicarbonate) or do I have to go out and buy a remineraliser from someone like JBL.

 

[dw1305]

H all,

if the K+ ions (which will contribute to conductivity) are being exchanged for H+ ions (which don't) the conductivity should rise initially and then fall as the K+ ions are exchanged for H+ ions.

This bit is actually incorrect. The H+ ions also conduct electricity. "Regani" a chemist (who also keeps Apistogramma) <"explains why on this thread">.

You go to you local fish shop, buy some RO water from them, then add your Macro and Micro nutrients. So will these buffer the water (with a little bicarbonate)

Yes.

or do I have to go out and buy a remineraliser from someone like JBL.

No.

If you have hard tap water you can fulfil any calcium requirement by just cutting the RO with a small amount of tap water.

If you want a more scientific approach have a look on <"James' Planted Tank: Re-mineralising RO"> it gives recipes for raising both dGH and dKH.

cheers Darrel

.

 

[Staticrzr]

hey guys.. I'm in the same boat here.
I'm thinking of buying a RO unit as most of the journals which I follow and love here are using RO water. The other reason I'd that my water here is very very hard.

I know for a fact that Viktor from GreenAqua is using salty shrimp to remineralise his water. - he uses either his own EI recipe or ADA ferts.
I also know that Luis Cardaso is just using plain RO water with his own recipe of EI which just contains more than MgSO4.7H2O.

Given the fact that I never used RO water I'm in a crossroad.. which patch to choose? Maybe I'll get some input from some of you guys who are actually using RO.

 

[sciencefiction]

Darrel, this is really really useful. You know that I've had some disasters in my nano and am now pretty sure that was down to very very low dKH.

Definitely the disastrous case. Out of all "measures" the KH is the most important bit. It also gets used up in various processes, including nitrification so it needs replacing to keep the water stable. How much of it gets used up depends on the particular tank set up.

just measured my RO after re mineralization and PH was around 10. Thanks to Calcium Sulphate. Now I am not sure how shrimp safe this would be during water changes I know PH shock is a myth but going from PH 6 to PH 10 in water change seems a lot to me. Any advice on substitute for Gypsum and in what amount for 25L as for Jame's recipe?

Don't dwell on your Ph. When re-mineralizing water, get one of those TDS electronic test kits and mix the water to the same reading each time, providing you are using the same source of mixers, whether tap water or other dry stuff. The individual readings of Gh, Ph, etc will vary. You just need 1-2 dKH to hold the water stable and the same TDS reading after the water is mixed. If you try matching individual readings, it gets messy and mostly bad for the fish.

 

[Staticrzr]

hey guys.. I'm in the same boat here.
I'm thinking of buying a RO unit as most of the journals which I follow and love here are using RO water. The other reason I'd that my water here is very very hard.

I know for a fact that Viktor from GreenAqua is using salty shrimp to remineralise his water. - he uses either his own EI recipe or ADA ferts.
I also know that Luis Cardaso is just using plain RO water with his own recipe of EI which just contains more than MgSO4.7H2O.

Given the fact that I never used RO water I'm in a crossroad.. which patch to choose? Maybe I'll get some input from some of you guys who are actually using RO.

ok, I've done some more reading and this is what I have.
use RO water, add your EI solution based on the amount of water you have, check tds using a tds meter. If TDS showing lower than 120-> add salty shrimp and aim for tds 120-130.
You don't have to worry about pH if ur using soil similar with Ada Amazonia which keeps it pH stable at around 6.7-6.8.

Is this about right?