Thank you again Mr Burr. Could you please direct me to where you are getting your targets? I found the following from the Barr article:
CO2 range 25-35ppm
NO3 range 5-30ppm
K+ range 10-30ppm
PO4 range 1.0-3.0 ppm
Fe 0.2-0.5ppm or higher (?)
GH range 3 degrees ~ 50ppm or higher
where there is clearly no reference to Mg. Also, if I do add the 6 tsp of MgSO4 as you suggest, I get from Rotala Butterfly 3.45 ppm of sulfur with the addition of K2SO4 as well. Is that too much sulfur? Again no guideline I have found for sulfur either.
I appreciate your time and help.
Well, 6 tsp MgSO4 wasnt my suggestion, it was Barr's in the recipe you were trying to duplicate, which adds approximately 1 ppm per dose
There is no clear cut EI recommendation for Ca and Mg. Both combine to make up dGH and are considered somewhat relative to each other. Generally speaking you want to keep a ratio between 5:1-3:1 Ca:Mg.
So for example if you're using RO water and reconstituting with 10-15 ppm Ca, you may only need 3-5 ppm Mg. If your using all tap with 40 ppm Ca (like me) you probably want closer to 10-12 ppm Mg
Mg, along with Ca is generally dosed 1x week right after water changes. In my case I dose 7 ppm in one whack and forget about it (tap contains about 4 ppm)
Barr's inclusion in the macro mix is fine too. His recipe adds 1 ppm per dose, so an additional 3 ppm per week. That's enough to make a difference and should cover the Mg base for most people. Including it in the macro mix is more for convenience than anything
As for how much S is to much, note that these SO4 compounds add sulfate (SO4) not sulfur (S) The calculator shows the S equivalent of SO4. It does the same for N and P when calculating for NO3 and PO4. KNO3 for example doesnt add any actual N, the calculator just shows you the N equivalent for whatever ppm of NO3
The multiplier for S = SO4 is 3.
* None of this is really important to understand just bear with me
What your actually getting from 6 tsp MGSO4 is 10.35 ppm SO4 (3.45 x 3)
To answer your question
- Sulfur/Sulfate is an important secondary nutrient that plants need, and actually use a lot of. So it needs to be in the mix. The amounts we get from all these SO4 compounds are nothing to worry about. One of my best tanks ever ran consistently over 100 ppm (SO4)
Role of Sulfur in Plants
If you're using tap water that comes with already high amounts then it may be something to consider, otherwise dont worry about it.
I found the following targets from the Nilocg website:
Target Concentration Levels
NO3 7.5 ppm
N 1.694 ppm
PO4 1.3 ppm
P 0.424 ppm
K 5.3 ppm (7.5 ppm with additional K2SO4)
Fe 0.5 ppm
Mg 0.107 ppm
dGH 0.025 ppm
Cu 0.007 ppm
B 0.061 ppm
Mn 0.143 ppm
Mo 0.004 ppm
S (0.917 ppm with additional K2SO4)
Zn 0.028 ppm
This is where I am getting confused as Nilocg says target amount of Mg is .107 ppm. It is from this that I got the original 3/4 tsp of MgSO4. Any clarification on the general consensus of target amounts of nutrients would really be appreciated.
Nilocg's micro breakdown is just quoting the ppm of everything in csm-b if you dose it for .5 ppm of Fe. Those arent "recommended targets" for anything besides Fe.
Classic EI calls for .5 ppm Fe 3x per week. He's selling csmb and telling you what you get from a .5 dose. That's all.
In the grand scheme of things that amount of Mg might as well be nothing. It just happens to be what's in a .5 dose of csmb.
EI was revised a few years ago to .2 ppm Fe 3x per week, down from .5. You'll notice rotalabutterfly gives values for .2 ppm Fe if you calculate for EI. Many folks still use the .5 routine and most "tsp charts" on the internet list it that way.
Personally I think somewhere in between is probably the sweet spot for most people, around 1 ppm Fe per week