Hi all,
Once you've got the percentage iron (Fe) you can use this both to work out how much you need to feed, and which source of chelated iron you have.
Because it is 13.3% Fe you have EDTA-FeNa.3H2O.
The workings for this are RMM 421 (C10H12N2O8FeNa.3H2O), so 10 x 12 (RAM C) for the carbon + 12 x 1 for H etc .
The RAM Fe = 55.85, so 55.85/421.1 = 0.1326 = 13.3% Fe
Then all you need to know is:
The volume of your tank
and the dilution factor to give you the amount of Iron in ppm.
I'll use a 100 litre tank, and 10cm3 of FeNa-EDTA solution just, because it makes the maths easier.
10cm3 = 1:100 dilution per litre, 10cm3 in 100 litres = 1 in 10,000 dilution.
Then 7.54g of FeNa-EDTA supplies 1g of Fe (as Fe3+). 1g of Iron diluted in 1000cm3 water = 1 in 1000 = 1000ppm.
You have a 1000ppm stock solution which you will dilute by 1 in 10,000, 10cm3 of the 1000pm stock solution supplies 0.1ppm Fe in 100 litres. I'd probably go for a bit more iron, so I'll make it 5000ppm stock, 5 x 7.54g = 37.7g.
So 37.7g of FeNa-EDTA made up to 1000cm3 in water stock solution, and that stock solution used at 10cm3 in 100 litres supplies 0.5ppm Fe3+.
cheers Darrel