How important is sulphur for aquarium plants?

jaypeecee

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Hi Folks,

Dennis Wong on his site classifies sulphur as a macro nutrient. As far as I am aware, the only macro nutrients are nitrogen, phosphorus and potassium (aka NPK). Please see:

https://www.advancedplantedtank.com/adv_nutrients.html

He also includes calcium and magnesium. Here I want to focus on sulphur. Many fertilizers contain no (reported) sulphur with those from Tropica and Seachem (Flourish) being exceptions. Perhaps there are others. So, my question is - how important is sulphur for aquarium plants? And, what function does it serve?

JPC
 

Edvet

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Can't see it as a macro, i do add it as i add Mg ( MgSO4, some add K2SO4 as K source).
Classic macro are N, P, K ( and C, H, O), secondary are Ca, Mg and S of wich far less are needed.
 

jaypeecee

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Can't see it as a macro, i do add it as i add Mg ( MgSO4, some add K2SO4 as K source).
Classic macro are N, P, K ( and C, H, O), secondary are Ca, Mg and S of wich far less are needed.

Hi Edvet,

So you would agree that sulphur is important. And, of course, sulphur is present in MgSO4 and K2SO4. But so many commercial preparations omit sulphur. I recently bought TNC Complete which, to my disappointment does not include sulphur - according to TNC's analysis on their web site. Yamato Green, on the other hand, would appear to list sulphur in their product. According to their web site:

"Sulfur: Helps in chlorophyll production. Essential for healthy root growth. Stimulates rapid plant growth. Usually deficient in all but the hardest water areas".

Although I use remineralized RO water in my tanks, my tap water contains a mean sulphate level of just 48.40 mg/l. The remineralizing salts that I use do contain sulphate but I don't know how much. Do you have any idea what sulphate/sulphur level we should aim for in our planted tanks or is it trial and error?

JPC
 

jaypeecee

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Hi Folks,

First things first - I am not a plant biologist but I do like to understand what makes plants tick. So, I read and read. Although the following is taken from a non-aquarium web site, it speaks volumes:

"Sulphur is part of an enzyme required for nitrogen uptake and lack of it can severely hamper nitrogen metabolism".

The above is a quote from https://www.yara.co.uk/crop-nutrition/agronomy-advice/dont-forget-about-sulphur.

Any comments?

JPC
 

dw1305

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Hi all,
So, my question is - how important is sulphur for aquarium plants? And, what function does it serve?
It is important, but I would be very surprised if any of our tanks are deficient in sulphur (S).
"Sulphur is part of an enzyme required for nitrogen uptake and lack of it can severely hamper nitrogen metabolism"
That is right, we still live in a sulphur rich environment, post industrialization, if you were <"in Australia"> then these deficiencies are more likely, because you have very old soils and low levels of industrialization.
Although I use remineralized RO water in my tanks, my tap water contains a mean sulphate level of just 48.40 mg/l.
Do you have any idea what sulphate/sulphur level we should aim for in our planted tanks or is it trial and error?
But in levels needed it will be low, almost micro levels low.
Your 48 mg/L (48 ppm) is an order of magnitude more than the minimum requirements for the plants.
as i add Mg ( MgSO4....
That would be my answer to the question, a very small addition of Epsom Salts is going to cover any sulphur requirement.

cheers Darrel
 

jaypeecee

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Your 48 mg/L (48 ppm) is an order of magnitude more than the minimum requirements for the plants. That would be my answer to the question, a very small addition of Epsom Salts is going to cover any sulphur requirement.

cheers Darrel

Hi Darrel,

Many thanks for your reply.

From your two statements above, I have calculated that approximately 40 mg/l of Epsom Salts (MgSO4.7H2O) is required to provide approximately 5 mg/l of sulphur. Do you agree with my calculation?

Thanks in advance.

JPC
 

tiger15

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Dennis Wong is a plant guru, and I have yet found one statement he made that is inaccurate or I disagree with. Yes, sulfur, along with Ca and Mg, are macros but rarely mentioned as sulfur is in fish food and a complementary element of many other fertilizers such as CaSO4, MgSO4, K2SO4, FeSO4 and so on.
 

dw1305

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Hi all,
I have calculated that approximately 40 mg/l of Epsom Salts (MgSO4.7H2O) is required to provide approximately 5 mg/l of sulphur. Do you agree with my calculation?
Yes I do.

The RMM of MgSO4.7H2O is 246.5 and the RAM of sulphur is 32, so it is ~13% sulphur (and ~10% Mg).

Divide 5 by 40 = 12.5 ~ 13%.

If you had a 100 litre tank and you added 4g (400 mg) of Epsom Salts you've dosed ~4ppm of Mg and 5ppm of S.
we still live in a sulphur rich environment, post industrialization
sions-by-region-North-America-USA-Canada-East-Asia.png

(From "Global and regional trends....." 2019).

cheers Darrel
 

jaypeecee

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Hi all, Yes I do.

The RMM of MgSO4.7H2O is 246.5 and the RAM of sulphur is 32, so it is ~13% sulphur (and ~10% Mg).

Divide 5 by 40 = 12.5 ~ 13%.

If you had a 100 litre tank and you added 4g (400 mg) of Epsom Salts you've dosed ~4ppm of Mg and 5ppm of S.
sions-by-region-North-America-USA-Canada-East-Asia.png

(From "Global and regional trends....." 2019).

cheers Darrel

Hi Darrel,

Many thanks for confirming that.

BTW, there is a minor error in your last sentence - "4g (400 mg)" should read "4g (4000mg)".

JPC
 

dw1305

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Hi all,
BTW, there is a minor error in your last sentence - "4g (400 mg)" should read "4g (4000mg)".
Thank you, there is another post somewhere with the same error. I know there are a 1000 mg in gram, so I'm blaming the keyboard.

cheers Darrel
 

jaypeecee

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Hi Folks,

Just an extra snippet of information that may, or may not, be useful to others. I added 5g of Epsom Salts to my 125 litre tank. This raised the GH by 1.5dH and raised the conductivity by 29 microSiemens/cm.

JPC
 

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