Remineralizing RO Water

[tam]

I just wanted to add in that I've used them too, as much as it might have saved a few pounds... but not a lot as a smallish tank and low water change % so not going through it. It's just feels easier over having to mix from a few containers... source from suppliers in bigger quantities, worry if you're doing it right etc.

It's good there are cheaper alternatives but don't feel bad if buying a tub takes away something that would add a hassle for you and therefore makes your hobby more enjoyable. Some people love that aspect of DIY, others don't. There are lots of ways to save money from waiting longer for plants to grow in to spawning your own fish. Just pick what priorities work for you.

 

[MichaelJ]

It's fairly well acknowledged that is exactly what they are. In fact I believe it has been noted that given how easily they dissolve, they are the most likely the slightly less desirable Chloride based variants (MgCl2 and/or CaCl2). They may add a little KCl too, but the 'trace elements' will largely be impurities in the main salts.

Totally agree @Wookii . As a matter of fact if you want to keep TDS as low as possible for a given GH (E.g. if you keep shrimps 😉 ) you want to use CaSO4 (Gypsum salt) / MgSO4 (Epsom Salt) or just cut it with plain tap if its otherwise good and mainly CaCO3. If not, and if TDS is of no concern, or you want to pre-batch your Calcium/Mg (GH) solution, CaCl2/MgSO4 is what you want to use due to its much higher solubility. If you use CaCl2 just make sure it's not exposed to air when stored as it is highly hygroscopic (sucks up moisture from the air). As far as the additional "minerals" in Salty Shrimp and Shrimp King GH; whatever they "add" (if not just impurities as @Wookii said) in addition to Ca and Mg is of no significance to the shrimps. Whatever additional minerals the shrimps need they will get from their food.

Just in general; be careful when referring to TDS ppm's and remineralization - you have to actually measure the GH or better, KNOW what quantities your adding to the water in terms of Ca and Mg to establish the correct GH. Also a TDS measurement depends on the conversion factor from EC to ppm used by the TDS meter - EC in uS/cm which our TDS meters are actually measuring - the factor will typically be anything from 0.5, 0.64 or 0.7. The TDS ppm's you get from a solution will not really match the actual ppm - only a gravimetric analysis can establish the true ppm of an evaporated solution (or you can calculate it if you know the molar mass etc. of the compounds you are using). I have probably written well over a hundred posts on the topic on UKAPS over the years - I wish I had Darrels (@dw1305) skills to sprinkle my post with references and links to some of the better ones 🙂

Cheers,
Michael

 

[Iain Sutherland]

I wish I had Darrels (@dw1305) skills to sprinkle my post with references and links

He is the link Master of the Universe! 🤓

 

[hamfist]

Just in general; be careful when referring to TDS ppm's and remineralization - you have to actually measure the GH or better, KNOW what quantities your adding to the water in terms of Ca and Mg to establish the correct GH. Also a TDS measurement depends on the conversion factor from EC to ppm used by the TDS meter - EC in uS/cm which our TDS meters are actually measuring - the factor will typically be anything from 0.5, 0.64 or 0.7. The TDS ppm's you get from a solution will not really match the actual ppm - only a gravimetric analysis can establish the true ppm of an evaporated solution (or you can calculate it if you know the molar mass etc. of the compounds you are using). I have probably written well over a hundred posts on the topic on UKAPS over the years - I wish I had Darrels (@dw1305) skills to sprinkle my post with references and links to some of the better ones 🙂

Yes, completely agree.
However, for simplicity and ease of making up new water, once one has mixed up your first batch of SS GH+ in RO and actually got the GH to where you want it to be, according to a good GH test (this is the step I failed to mention in my initial post), you can then measure the TDS. Thereafter, if you use the same TDS pen each time, all you need to do with further batches is add SS GH+ to get that same TDS, and you will know that the GH is right. It just so happens that my TDS pen seems to correlate pretty well with the correct 17.9 ppm per degree GH conversion (ie. it measures roughly an extra 18 ppm for each extra degree of GH of the GH+ remineraliser I add (according to the API liquid GH test).

 

[dw1305]

Hi all,

Its such a shame that companies such as Salty Shrimp (with Seachem being probably the worst offender) use secrecy as a deliberate marketing tool.

They do, their aim is to <"obscure the truth"> using conjecture and some very carefully worded blurb.

I would love to know the genuine, and not just the alleged, composition of course

I will bet that it will be some combination of cheap and <"easily available compounds">.

Once you are past the design of the container you buy them in, there isn't any issue of <"aesthetics with fertilisers etc">. Ions don't "know" which compound they originated from. As an example every calcium (Ca++) ion on Earth has been combined in a multitude of different compounds during the ~7 billion years since they formed in the nuclear furnace of an imploding massive Yellow Giant star - <"NOIRLab: Astronomers Sink Their Teeth Into Special Supernova - AURA Astronomy">.

And do the company actually even know what those trace elements are or are they simply mainly contaminants ?........ I would also love to know the composition of the almost (alleged) 0.5% trace elements in SS GH+

You can get <"analytical grade chemicals">, with a high degree of purity, but they are very expensive. For a lot of chemicals there is any value in refining them any further than is required, so they have a certain degree of impurity left from their manufacturing process.

This is <"Calcium chloride - Wikipedia">

In much of the world, calcium chloride is derived from limestone as a by-product of the Solvay process, ...... In the US, most calcium chloride is obtained by purification from brine. As with most bulk commodity salt products, trace amounts of other cations from the alkali metals and alkaline earth metals (groups 1 and 2) and other anions from the halogens (group 17) typically occur.

cheers Darrel

 

[dw1305]

Hi all,

Just in general; be careful when referring to TDS ppm's and remineralization - you have to actually measure the GH or better, KNOW what quantities your adding to the water in terms of Ca and Mg to establish the correct GH.

I usually assume (the basis for these assumptions is in <"Guide to TDS">):

• That you get 1 : 1 dGH : dKH (from dissolved limestone (CaCO3)) in UK tap water, and
• that the dGH is overwhelmingly from calcium (Ca++) ions, and
• that conductivity and Ca++ and 2HCO3- ions are (approximately) positively correlated.

But these are all assumptions and ones that may not hold true for other areas, away from the S. of the UK.

Whilst dGH and dKH are linked using <"hard water as your remineraliser">, you can <"decouple them"> with your own designer mix.

cheers Darrel

 

[dw1305]

Hi all,
@hamfist you should be able to get tap water hardness figures from your water company -<"Home - Southern Water">, but it will be about 17- 18 dGH & 17 - 18 dKH <"for geological reasons">.

Our water (above) (just E. of Bath) is from a limestone aquifer <"and pretty consistent through the year">, if you have some surface water it will be a bit more variable.

However, for simplicity and ease of making up new water, once one has mixed up your first batch of SS GH+ in RO and actually got the GH to where you want it to be, according to a good GH test (this is the step I failed to mention in my initial post), you can then measure the TDS.

If you didn't want to use your tap water as a remineralising agent? Rather than relying on the GH test strips I'd go the other way around and make a standard solution and then test that with the strips.

If you wanted a quick and dirty calibration? You could just use your tap water, or buy some mineral water of known chemical composition - <"French Click - Badoit Verte 6x1L">. I used to do this for work, and just wander around a few supermarkets until I'd bought "spring water" with a range of mineral contents.

The derivations and formulae you need are in Larry Frank's <"The Krib"> article linked here: <"Confusion concerning 0dKH and nitrification">

You could add calcium chloride (CaCl2.2H2O) and magnesium sulphate (MgSO4.7H2O) to RO water to give you a standard solution of known dGH. They are both salts that are cheap to buy (£5 / kg) for culinary, or health, reasons.

cheers Darrel

 

[Rich Jackson]

I’d use magnesium sulphate and calcium sulphate. 3:1 ratio of Ca:Mg, and raise to a GH of 6.

Where are you getting these from ?

 

[hypnogogia]

Where are you getting these from ?

I think I got mine from APC Pure, but you'll probably find them on eBay as well.

 

[hamfist]

Just pricing it up on Ebay, 1kg of APC pure CaSO4. 2H20 is £16.64 delivered. 500g of MgSO4.7H20 is £6.55 delivered. Those 2 mixed together, adjusting for molecular weights etc, gives very close to a 3:1 mix of Ca:Mg. That'll give you 1.5kg of remineraliser. It would be no surprise if that is exactly what Salty Shrimp and SHrimp King actually do to make their GH+ product. If someone on here has any spare time they want to waste checking my maths please feel free. It would be nice to confirm that the relative mix I suggest of the 2 x compounds actually does produce the 3:1 Ca;Mg ratio one looks for.
I might be tempted to do that the next time I need remineraliser. Is the addition of K and Cl in the mix particularly important do you think, or done mainly for cost reasons ? Most of my tanks are equally Shrimp and plant-oriented these days.

 

[dw1305]

Hi all,

Those 2 mixed together, adjusting for molecular weights etc, gives very close to a 3:1 mix of Ca:Mg.

That's it, you just need to take into account the <"water of crystallization"> when you <"work out the percentage of the nutrient"> that you are interested in. It is worth noting that CaSO4.H2O has very limited solubility (2.6 g in 1 litre of water at 20oC), which is why remineralising compounds are usually dry dosed.

if you mixed 2g of CaSO4.2H2O and 2g of MgOS4.7H2O for every ~25 litres of RO water, you should be about right for 4dGH

I'm not too concerned <"with the exact calculation">. @Zeus. and @Hanuman <"have taken all the fun out of it"> with the <"IFC calculator">, but if any-one wants the maths............

Optional computation bit
The values we are interested in are:

• Calcium 7.143 mg / L (ppm) Ca = 1 dGH and
• 4.3 mg / L of Magnesium (Mg) = 1 dGH

They are different weights because of the differing RAMs of calcium (40.1) and magnesium (24.5), but both are 0.17832 mmol / litre and = 1 dGH. You can mix and match in that ratio, 2 dGH could be 14.2 mg Ca or 8.6 mg Mg etc or any mix of calcium and magnesium.

The RMM of CaSO4.2H2O is 142g / litre and 40 / 142 = 28% Ca and the <"RMM of MgSO4.7H2O"> = 246.5 and 24.3 / 246.5 = 10% Mg.

You then need to take into account,

• the differing RAM of calcium and magnesium and 4.3 / 7.14 = 0.6. So 1 mg of Ca adds the same amount of dGH as 0.6g mg of magnesium,, and
• the differing proportions of each element in their source compound, so 1g CaSO4.2H2O = 280 mg Ca and 1g MgSO4.7H2O = 100 mg magnesium.

I'll do the next bit in 10 litres, just to make the weights a bit bigger: If we add 1 g of each compound to 10 litres of water we've added 28 mg / l Ca and 10 mg / l Mg. Then we have 28 / 7.1 approx 4 dGH via calcium and 2.3 dGH via magnesium, approx. 6.3 dGH in total.

At that point a splash of tap water would add a bit more calcium and a smidgen of dKH. If you didn't want to do that? You could buy some potassium bicarbonate (KHCO3).

cheers Darrel

 

[MichaelJ]

Is the addition of K and Cl in the mix particularly important do you think, or done mainly for cost reasons ? Most of my tanks are equally Shrimp and plant-oriented these days.

This is all a plant consideration: K is a an essential macro nutrient (which should be dosed separately instead of relying on collateral from a re-mineralizer - sachem equilibrium being the absolute worst product in that department). Cl on the other hand, is a micronutrient (plants only need trace amounts). which is another reason not to use CaCl2 as you will get a ton of it even for a modest GH increase - probably why at least some expert plant growers shy away from It.

time, all you need to do with further batches is add SS GH+ to get that same TDS, and you will know that the GH is right.

Agreed. Pretty much my approach as well - we just need a fixed starting point for reference (datum).

Cheers,
Michael

 

[Maf 2500]

There is also calcium nitrate and magnesium nitrate if you want to avoid adding both chlorides and sulphates to your water.