Hi Dave - this is Cindy's husband - Robert..
The brand of Epsom Salts is not really as important as the purity.
So, just check the label make sure it's USP (United States Pharmacopeia (USP) )
This means you are getting the purity that's pretty much regulated and monitored by
some type of an authority - and this one is for standards for human consumption which
I can pretty much guarantee carries much more legal weight than technical grade substances
(like road de-icer salts) . (Magnesium Chloride)
do some of your own Google research using keywords "epsom salts FDA" and you will hit
some goods links with PDF files which are MSDS sheets from a company called PQ Corporation
which is one manufacturer of both Technical Grade, and USP (Pharmaceutical Grade).
Any Pharmacy which sells "Epsom Salt, Magnesium Sulfate, U.S.P. " should be suitable.
(We get ours at HEB pharmacy - just because that's convenient for us).
Again - use the calculator on the SeaChem Website for quantities to adjust per gallon.
And don't raise it more than 100 ppm/day. <-- This is important!
It wouldn't matter if you were using SeaChem's Magnesium Salt additive, or Epsom Salts USP
as far as the rest of the calculations go. - Just do the changes slowly, because each day it raises,
organisms are going to react. (Some things will start new growth spurts - but this means they will start consuming
Calcium and Magnesium and Strontium at an even faster rate than before). --But don't worry, this is usually
what we stony growers are after anyways, - just be aware that you are going to be altering the water chemistry,
and don't shock them - let them adjust.
It also takes time for the water to balance so I would wait 6 hrs after adding to re-test for Mg/Ca/KH levels.
Do you guys run Carbon? -We do, (Kent Reef Carbon - the pellets).
This is to remove any impurities in the additives (we don't trust the industry "completely" on the purity thing,
since nobody's watching (regulating) them like USP FDA., etc.
The purity of the Carbon is also just as important.
For all we know - someone could be bottling USP grade chemicals, and selling them, OR they could just as easily
be bottling technical grade chemicals (purity in question).
And - it's the impurities we wonder (worry) about.
We have observed the chemical content labels on one Manufacturers' brand (will remain nameless here, since this is
a public forum): and we note the Mg additive contains 2 types of Mg salts: Magnesium Sulfate, and Magnesium Chloride.
The interesting thing is - they don't give amounts like 50/50 or 75/25, or what... so for all I can tell, this could be
99% Epsom Salts (sulfate)and 1% Road de-icer (chloride).
There's no way of telling what they are doing, really.
At least with the Pharmaceutical grade stuff, we know the purity of what we are getting - check the labels.
Most USP labels I see show guaranteed analysis of 9.8 percent water soluble Magnesium. and 12.9 percent Sulfur.
Each molecule contains 1 sulfur Atom, 1 Magnesium atom , and 4 Oxygen atoms. (for your weight proportions),
so - yes you are buying a lot of oxygen..(in the salt) heh..