# Why sulphates?



## CryptKeeper (27 Mar 2018)

Outside the regular macro nutrients and traces, commercial additives and Tom Barr's GH booster seem to be based around various sulphates. I wonder why that is, why are sulphates beneficial? I'm thinking that if I'm dosing EI and wanted to raise GH and/or KH as well, wouldn't I rather add Ca(NO3)2 and KHCO3? That way I'd be adding useful nutrients (nitrate and potassium), and could even lower the KNO3 dosing accordingly.

What am I missing?

I'm asking because my tap water is very soft (catchment water) with Ca around 15mg/l and alkalinity low enough that CO2 injection rapidly drops the pH to the low 5's. I'm currently adding Epsom salts as per the EI dry salts article, but I think I ought to add some calcium as well. I'd also like to raise the alkalinity because right now dosing CO2 (or even just measuring pH and CO2) is very tricky and sensitive.


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## Zeus. (27 Mar 2018)

CryptKeeper said:


> Outside the regular macro nutrients and traces, commercial additives and Tom Barr's GH booster seem to be based around various sulphates. I wonder why that is, why are sulphates beneficial? I'm thinking that if I'm dosing EI and wanted to raise GH and/or KH as well, wouldn't I rather add Ca(NO3)2 and KHCO3? That way I'd be adding useful nutrients (nitrate and potassium), and could even lower the KNO3 dosing accordingly.
> 
> What am I missing?



Is not the sulphates we are after its the elements to which the sulphates are ironically bonded to which we are after. eg I add quite a bit of MgSo4 to my EI mix purely for the Mg, when the MgSO4 is in water it dissolves due to its week inonic bonding and the plants can pickup the Mg. Sulphates are chosen for making the salt due to its relative mass for gain in [Mg] and the product dissolves in water.

Well thats my understanding 

Hope it helps


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## CryptKeeper (27 Mar 2018)

Zeus. said:


> Is not the sulphates we are after its the elements to which the sulphates are ironically bonded to which we are after.



That's exactly what I'm thinking, too, no inherent value to the sulphate ions. Why does everybody use calcium sulphate in their GH boosters then instead of calcium nitrate? They're both cheap and readily available.


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## dw1305 (27 Mar 2018)

Hi all, 





CryptKeeper said:


> I'm thinking that if I'm dosing EI and wanted to raise GH and/or KH as well, wouldn't I rather add Ca(NO3)2 and KHCO3?


You can do. Have a look at <"James' Planted Tank">. 





CryptKeeper said:


> I wonder why that is, why are sulphates beneficial?


Plants have a <"sulphur requirement">, but you are always going to fulfill that.

Generally the reason is that <"sulphates and nitrates are soluble">, whereas most <"carbonates, phosphates etc."> aren't once you get away from the group 1 (alkali metals), (so potassium bicarbonate (KHCO3) is soluble).





CryptKeeper said:


> I'm asking because my tap water is very soft (catchment water) with Ca around 15mg/l and alkalinity low enough that CO2 injection rapidly drops the pH to the low 5's......I'd also like to raise the alkalinity because right now dosing CO2 (or even just measuring pH and CO2) is very tricky and sensitive.


Do you have a drop checker? The pH changes due to an alteration of the CO2 ~ HCO3- ~ 2CO3~ pH equilibrium aren't the <"same as the pH changes"> caused by alteration in the water chemistry in harder (carbonate buffered) water. Because pH is a ratio (H+ ion donors : H+ ion acceptors) in very soft water pH is inherently unstable and will vary widely even with very small additions of acids or bases.

There is a lot of misinformation on forums (I know this is a forum) about pH and pH stability, but you can't extrapolate from hard water to soft water, and pH is an intrinsically quite a strange measurement. 





CryptKeeper said:


> Why does everybody use calcium sulphate in their GH boosters then instead of calcium nitrate? They're both cheap and readily available


It is only really aquascapers who add nitrates to their tanks, but you are right, any calcium ion in solution is the same as any other calcium ion.

A Ca++ ion is the same whether it came from calcium nitrate (Ca(NO3)2.4H2O) or calcium sulphate (CaSO4.2H2O), calcium nitrate is a lot more soluble as well. You need to add in the <"water of crystallisation"> when you work out the calcium content of a hydrated salt.

cheers Darrel


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## CryptKeeper (27 Mar 2018)

Thanks Darrel, your response is much appreciated. Nothing wrong with either sulphates or nitrates, then. I'll just do the numbers to make sure my overall NPK are non-limiting.

The KH thing is more vexing to me (unrelated to sulphates, of course). Among the things swirling around my head right now is the question whether or not I even _should_ raise the KH at all? I'm coming from a tradition of test kits and pH-Up/pH-Down tank maintenance 



dw1305 said:


> Do you have a drop checker?



Not yet. None of the LFSs in my area had any in stock, but I've got one coming in the mail. Hopefully soon, because right now I'm really just guessing. Measuring very low KH is probably inherently difficult and fraught with error (I'm using the Salifert KH alkalinity kit), and the pH-KH-CO2 charts don't even go down to the pH values I'm measuring. The Rotala Butterfly calculator returns hundreds of ppm of CO2, which I find hard to believe. There must be something else (soil substrate?) that affects the pH. A drop checker with 4dKH solution will hopefully bring some clarity about my CO2. Thankfully there isn't any fauna to kill yet (day 11 of a new tank).



> The pH changes due to an alteration of the CO2 ~ HCO3- ~ 2CO3~ pH equilibrium aren't the <"same as the pH changes"> caused by alteration in the water chemistry in harder (carbonate buffered) water. Because pH is a ratio (H+ ion donors : H+ ion acceptors) in very soft water pH is inherently unstable and will vary widely even with very small additions of acids or bases.



And would it be reasonable to assume that this isn't a problem in a planted tank with some fish and shrimp (nothing out of the ordinary)? Because if there is no point in raising the KH I won't be adding the KHCO3. The less the better. I'd still be dosing some Mg and Ca, as sulphate and nitrate, respectively.


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## ceg4048 (27 Mar 2018)

You cannot determine the level of CO2 in the tank based on the pH-KH-CO2 charts, so there is no point even worrying about that issue.
There is no point in adding KH just for the sake of KH. As noted one only needs to increase the alkalinity in order to be able to measure pH.
A KH of 4 is all one needs.

Ca is a micronutrient 15 ppm is fine. there is no point in adding more but there is also no harm.

The dropchecker is to be filled with distilled or RO water adjusted to 4 dKH. If your tank water is also 4 dKH then you will be fine and you really need not worry about how much the pH drops due to CO2. Neither the fish nor the plants will care.

As I constantly implore, please keep things as simple as possible. That way tank husbandry is less tedious and you are less likely to get things confused.

Cheers,


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## dw1305 (27 Mar 2018)

Hi all, 





CryptKeeper said:


> Among the things swirling around my head right now is the question whether or not I even _should_ raise the KH at all? I'm coming from a tradition of test kits and pH-Up/pH-Down tank maintenance


You don't actually need much dKH, I have some dKH/dGH, but that wasn't entirely by design, I've always used rain-water in the tanks and the geology here is limestone (CaCO3) so the rain-water picks up enough soil dust to give ~2dKH. I can use a dash of our tap supply (~18dKH) to add hardness, but if I couldn't a small addition of <"oyster shell chick grit"> (sold for chicken and caged birds) would do the job, or food grade potassium bicarbonate (KHCO3) etc.

I don't measure dKH directly (I have done in the past, using an acid/base titration in the lab.) but I use electrical conductivity as a proxy. I like low range (0 - 1999 microS.) conductivity meters, they work accurately over a whole range of water conditions and conductivity is a linear measure from RO water, at ~10 microS, all the way up to seawater at 53,000 microS (53 milliS).   

I'm not a big fan of most test kits, some are better than others, but it is actually quite difficult to get accurate figures for some of the nutrients we are interested in.

The situation with pH buffers is a lot more straight-forward <"they don't really have any practical application in fish keeping">. I have a bit of a problem with some of the companies that sell these products, who seem to write their product descriptions, presumably with the aid of a lawyer, to mislead and obscure what their products contain and how they work.

cheers Darrel


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## CryptKeeper (28 Mar 2018)

ceg4048 said:


> You cannot determine the level of CO2 in the tank based on the pH-KH-CO2 charts, so there is no point even worrying about that issue.
> There is no point in adding KH just for the sake of KH.



Thanks, that's good enough for me!



> Ca is a micronutrient 15 ppm is fine. there is no point in adding more but there is also no harm.



Ok, noted. How about Mg? My tap water has about 5mg/l. I'm adding Epsom salts (1/2 tsp three times a week to my 120l tank), can I stop that?

I wish there were some easy to use guidelines for identifying nutrient deficiencies, but I suppose it's not that simple. A lot of the deficiencies I've seen described for different nutrients look very similar to each other...



> The dropchecker is to be filled with distilled or RO water adjusted to 4 dKH.



My shiny new drop checker just arrived, I can't wait to put it in tonight. It comes with a 4dKH calibrated indicator solution.



dw1305 said:


> The situation with pH buffers is a lot more straight-forward <"they don't really have any practical application in fish keeping">. I have a bit of a problem with some of the companies that sell these products, who seem to write their product descriptions, presumably with the aid of a lawyer, to mislead and obscure what their products contain and how they work.



Yep, the pH-Up and pH-Down products are often the first things that greet you as you walk into chain aquarium stores. Along with admonitions about how deadly pH swings are for fish.

I'm a child of 80's and 90's aquaristics, there is a lot I have to unlearn. I really appreciate the clarity you guys are providing, it's like a fog is slowly lifting


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## dw1305 (28 Mar 2018)

Hi all,





CryptKeeper said:


> Ok, noted. How about Mg? My tap water has about 5mg/l. I'm adding Epsom salts (1/2 tsp three times a week to my 120l tank), can I stop that?


I'd probably carry on for the while, it isn't going to hurt. You could try cutting down to 1/2 tsp once a week. 





CryptKeeper said:


> I'm a child of 80's and 90's aquaristics, there is a lot I have to unlearn.


That it is it really, we all carry a <"lot of baggage"> from our fish keeping past.

Because I came back to fish-keeping from ecology/botany/horticulture, and working on the remediation waste water, it allowed me to look with new eyes at the advice being offered to aquarists.

I knew a reasonable amount about the scientific method, plant grow-lights and biological filtration (including phyto-remediation) and that allowed me to critically evaluate the advice given about them. If that advice was reasonably accurate I would give that author/forum more credence in areas where I didn't have any expertise.

Have a look at <"maxing CO2 in low tech...">. It doesn't relate to the original question, but it covers a lot of "un-learning"

cheers Darrel


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## ceg4048 (29 Mar 2018)

CryptKeeper said:


> Ok, noted. How about Mg? My tap water has about 5mg/l. I'm adding Epsom salts (1/2 tsp three times a week to my 120l tank), can I stop that?


As Darrel mentions, you can just carry on adding the MG that you are adding and at some point, try deleting the addition. Mg is also a micro nutrient so you only need microscopic amounts. Epsom salt is most useful for RO and soft water homes when the Mg content is virtually absent.



CryptKeeper said:


> I wish there were some easy to use guidelines for identifying nutrient deficiencies, but I suppose it's not that simple. A lot of the deficiencies I've seen described for different nutrients look very similar to each other...


Well in almost all cases it is actually very easy. 
The troubleshooting procedure is very basic when it comes to aquatic plants, but many hobbyists are fooled into thinking that the symptoms that appear for terrestrial plants are the same under water. They then start to try and decipher the symptoms and they almost always misdiagnose.

Here is an easy summary and procedure that will get you started and will give you a better chance of success.

1. Rule #1 is to ignore any of the deficiency charts you see scattered around the internet that are essentially guides for land plants.

2. By far, the most common deficiency in planted tanks, even in CO2 injected tanks or in tanks using other carbon enrichment methods is ironically, CO2. Melting leaves, distorted leaves, holes in leaves, stunted leaves, browning in leaves or stems, translucency of tissue, brown spots, black spots, disintegrating tissue, falling leaves (especially lower leaves) and any other structural anomalies exhibited anywhere on the plant is due to a Carbon shortfall. Carbon is the dominant element in plant tissue and therefore any shortfall of this element is immediately revealed as damage, deformation or necrosis of the tissue. Carbon shortages also triggers all forms of filamentous algae, most commonly, Hair Algae. Poor CO2 can trigger Green Spot Algae (GSA), Black Brush Algae (BBA), Cladophora Algae, Green Dust Algae (GDA), Oedogonium Algae, Rhizoclonium Algae and Staghorn Algae.

As you can see, this covers about 90% of the problems you will ever see, so this makes it very easy to diagnose.
How you fix a Carbon shortage though, is not easy and in fact is the most difficult procedural aspect of planted tanks.

3. Micronutrient shortages are rarely, if ever, the cause of algal blooms and their shortages can easily result in pale or yellowing leaves. Since almost all the micronutrients first appear as discoloration of YOUNG leaves that makes the diagnosis fairly easy, however, it's not really necessary to know specifically which one is the cause.
To avoid that complication you simply add more of the micronutrient mix(es), which will cover all of them, i.e. Iron, Magnesium, and so forth. Do not try and determine which - just add more of all of them. Too many people waste time and energy attempting precision. This is a useless strategy.

Also, if you are already adding the recommended amount(s) of micronutrients, and yet still experience these symptoms that tells you immediately that either your flow and distribution techniques are at fault or that the tank water is hard and that the chelation being used is failing so that the nutrients precipitate out of solution before getting to the plants. You should be able to see the precipitate though as it will give the water a tinge of yellow, brown or green for a few hours after dosing until the precipitate falls to the ground or is picked up by the filter.

3. Nitrogen shortage are revealed as yellowing or other forms of discoloration of MATURE leaves. The similar diagnosis applies here; if you are adding the prescribed amounts of Nitrogen and if the symptoms appear, then you need to review flow/distribution. No precipitate issues arise in this case.

4. Phosphorous shortage can result in stunting, but most often appears as Green Spot Algae (GSA). As noted in Item 2. GSA can also be caused by CO2 so when examining the tank  as a whole look for other symptoms of CO2 shortages so that you can separate PO4 shortage from CO2 shortage. As with the other nutrients, if you are adding the prescribed amounts and still experience the symptoms, then flow/distribution must be reviewed.

5. Potassium shortage is the most difficult to assess as this nutrient is used in almost every function of the plant. So for example Potassium is needed in order for the plant to uptake NO3. Potassium is also responsible for maintaining turgidity and the pH of the cell and tissue between 7 and 8. Outside the acceptable range many plant functions cease. So a shortage may appear as a Nitrogen shortage or may appear as stunting. To get around this complication dose a Potassium based salt for Nitrogen and for Phosphorous such as KNO3 and KH2PO4. This will ensure that there is more than enough K. If using other forms of N, such as Urea or Ammonium Nitrate then ensure that other Potassium salts are added such as KH2SO4.

Hope this helps to simplify because dosing NPK+micros is meant to be the easiest of all things planted.

Also please review the Dropchecker article in the Tutorials section.

Cheers,


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## CryptKeeper (29 Mar 2018)

Fantastic, thanks for the mini tutorial. I really appreciate the time you guys are putting into this.


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