# Acceptable sulfur levels?



## Skizhx (Oct 12, 2010)

What are acceptable sulfur levels for the aquarium? I've been unable to find any info specifically related to this.

Basically I'm finding that KNO3 dosing has been putting my nitrates higher than I'm comfortable with. Furthermore, I use CaNO3 as a calcium source and MgSO4 as a magnesium source.

So my plan is to reduce/eliminate my dosing of KNO3 and substitute K2SO4 as a potassium source (alongside KHPO4 which I'm already dosing, but that's not _too_ relevant to this question).

So if I could know what level of sulfur I want to stay below, that would be a big help for me working out appropriate dosing levels. Thanks!


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## JustLikeAPill (Oct 9, 2006)

I don't think people people usually worry about sulphur/sulphate. I don't. 

I dose a dash of potassium sulphate once a week on my 60-P.


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## Skizhx (Oct 12, 2010)

Is that because the toxic levels are so high that you'd probably never reach them? Or because people rarely dose much/any sulphate though?


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## Seattle_Aquarist (Mar 7, 2008)

Hi Skizhx,



> Content in dried sample: Sulfur content ranges between 0.15% - 0.5% . Some plant types will accumulate 3 times the sulfur to P level but more frequently S and P levels are similar.​


Sulfur is considered a "macro" nutrient and is thought to be associated with disease resistance. In dried terrestrial plant samples the sulfur : potassium ratio varies from 1:1 to 3:1.

Seachem Flourish Comprehensive, which I considered a balanced fertilizer, has a sulfur percentage about 2/3 the potassium percentage. I dose Potassium Sulfate (K2SO4) in conjunction with KNO3 and KH2PO4 as part of my "macros".


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## Skizhx (Oct 12, 2010)

Thanks seattle, just a quick question though, your quote states



> Some plant types will accumulate 3 times the sulfur to P level but more frequently S and *P *levels are similar


But then you start talking about potassium ratio.

Who's mixing what up here? Did they mean K instead of P? Or did you get them mixed up when you were writing your post?


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## Seattle_Aquarist (Mar 7, 2008)

Hi Skizhx,

Thank you for noticing my error; I apologize if I caused confusion. You are absolutely correct; I was substituting Potassium for Phosphorus in part of my post.

This part is correct:


> Content in dried sample:
> Sulfur content ranges between 0.15% - 0.5% . Some plant types will accumulate 3 times the sulfur to P level but more frequently S and P levels are similar.


In Seachem Flourish Comprehensive the analysis (on select nutrients) is:

Total Nitrogen 0.07%
Available Phosphate ( P2O5) 0.01%
Soluble Potash 0.37%
Sulfur (S) 0.2773%


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## Skizhx (Oct 12, 2010)

Happens to me all the time 

Thanks for the help as always


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## wet (Nov 24, 2008)

Skizhx said:


> Is that because the toxic levels are so high that you'd probably never reach them? Or because people rarely dose much/any sulphate though?


This page http://pmep.cce.cornell.edu/profiles/extoxnet/pyrethrins-ziram/sulfur-ext.html says:


> The 96-hour LC50 values for two fish species, bluegill sunfish and rainbow trout, are greater than 180 ppm in a study using a 99.5% sulfur dust formulation. The 48-hour LC50 for daphnia and the 96-hour LC50 for mysid shrimp is reported to be greater than 5,000 and 736 ppm, respectively, in a study using 90% sulfur (9, 10). In studies on ecological effects involving two fish species, daphnia, and mysid shrimp, sulfur has been shown to be practically non-toxic to the species tested (1, 3, 7, 8 ).


So, fwiw, these guys add to collective experience and say it's a little bit of both. It takes alotta K2SO4 CaSO4 and other stuff to get to 700-5000ppm, and these are relatively sensitive fish, and it's hard to imagine a hobbyist ever getting to these levels.

(LC50 is half the lethal concentration (LC). LC50 is considered "safe".)

In terms of plants, this is an interesting thread where the original poster has pics and folks who can grow plants (ie HeyPK, goldier, EDGE) point to S toxicity. Note that genetao is dosing around 100ppm of Sulfur.
http://www.aquaticplantcentral.com/...933-what-deficiency-pictures-56k-warning.html


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## genetao (May 10, 2008)

What Ray said^

I did experience a Sulphate toxicity build up over several months, just by dosing a little bit more than 1/4 tsp of K2SO4 into a 10 gallon tank (which in actuality is only 8.5 gallons of water). 

I started noticing pinholes and thought I didn't dose enough potassium. So when I upped the K2SO4, things got really bad. Once I found out that it was SO4 toxicity build up, I dramatically cut back on K2SO4, and things look sooooooo much better.


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