Originally Posted by Seattle_Aquarist
Lets continue to do the math.
aquariumfertilizer.com Ferrous Gluconate
8 oz equals 226.8 grams
20 grams makes 62.5ml
Therefore 8 oz makes 226.8/20 X 62.5 or 708ml
$12.00 for 8 ounces divided by 708ml equals $01.7 per ml.....The math checks out.
The mixing instructions on AquariumFertilizer.com are kinda crazy -- I wonder where they came up with that?
If you're going for a solution 10,000 ppm Fe by mass, it can also be thought of as a 1% Fe solution (10,000/1,000,000 = 0.01, or 1%). So of the full mass of the solution, 1% comes from the mass of the iron.
A 250ml bottle of the solution will weigh roughly 250g, as the density of water is roughly 1g/ml, and the solution is mostly water. 1% of 250g is 2.5g.
So we need enough gluconate to get 2.5 g of iron. Typically, most Fe Gluconate you find for sale is about 12.5% iron, so 2.5g/0.125 = 20.0g Fe Gluconate per 250ml bottle.
The half-pound (226.8g) of gluconate will then make 226.8g/20.0g = 11.34 250ml bottles of 1% Fe solution.