Some GH Boosters contain Fe and some don't. Seachem's Equilibrium, Grumpy's GH Booster and The Ultimate GH Booster contain Fe while Barr's GH Booster and Kent Marine's R/O Right do not contain Fe according to the info that I found.
Guaranteed Analysis - Equilibrium: http://www.seachem.com/Products/product_pages/Equilibrium.html
Soluble Potassium (K20) 23.0%
Calcium (Ca) 8.06%
Magnesium (Mg) 2.41%
Soluble Iron (Fe) 0.11%
Soluble Manganese (Mn) 0.06%
Derived from: potassium sulfate, calcium sulfate, magnesium sulfate, ferric sulfate, manganese sulfate. Elemental potassium is present at a concentration of 195,000 ppm (19.5%). Archaic fertilizer laws force us to list potassium in terms of equivalence to a material that is not present (K2O) rather than the more scientifically sound method of simple elemental equivalence.
Grumpy's GH Booster: http://www.bestaquariumregulator.com/dosing.html
* 5 grams will add the following to 10 gallons of water:
* 25 ppm K+
* 39 ppm CaCO3 hardness equivalent (just over 2 dGH) (breaks out as 26.6 ppm Ca as CaCO3 and 12 pppm Mg as CaCO3)
* 12 ppm Mg
* 0.15 ppm Fe
* 0.07 ppm Mn
* And will raise the GH just over 2 dGH.
The Ultimate GH Booster: http://www.greenleafaquariums.com/aquarium-fertilizers-supplements/gh-booster.html
Description - Contains:
* Potassium Sulfate (K2SO4)
* Calcium Sulfate (CaSO4)
* Magnesium Sulfate (MgSO4)
* Iron Sulfate (FeSO4)
* Manganese Sulfate (MnSO4)
Barr's GH Booster: http://aquariumfertilizer.com/index.asp?Option1=inven&EditU=2&Regit=7
This is Tom Barr's Poor Man's GH Builder/Booster. Barr's GH Booster contains: Potassium Sulfate, Calcium Sulfate, Magnesium Sulfate.
KENT MARINE R/O RIGHT: http://www.kentmarine.com/products/kent-ro-right.htm
Kent Marine Powdered R/O Right is a specially formulated mixture of dissoluble solids (also called general hardness or GH) which includes major salts of sodium, magnesium, calcium, and potassium together with all necessary minor and trace minerals, together with a small amount of carbonate alkalinity (KH) to reproduce artificial river water (most aquarium fish are river fish). Provides natural water chemistry for the conversion of reverse osmosis, distilled or deionized water for fresh water fish and plants. Provides a balanced electrolyte system. Useful for all fresh water fish, including Discus. This is the premium dry formula used by the world over to raise discus and other freshwater species. Contains no phosphates, nitrates, silicates or organic chemicals to pollute the system! R/O right is unmatched for quality and value! From:
http://www.marinedepot.com/Kent_Mar...ents-Kent_Marine-KM5333-FWADRO-KM5333-vi.html
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