Vitax 5SQI20 2 x 20 g 10.0 x 4.0 x 17.0 cm Sequestered Iron Plant Tonic

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Hi, I have two question both involving calculations, I must add I am not a chemist, but I really could use the help. I my tank is low tech/low light and I have very hard water living in Colchester. Our compound is 2% Fe which means that 1 g of chelate contains 0.02 g of Fe. After that there are 1000 mg in 1 gram (10 So our fertiliser has 20,000 ppm of Fe. If we take 1g of "Chempak sequestered iron" and add it to 1 litre of water, we've divided 20,000/100, so we have 20 ppm Fe. You have a 450 litre tank, so we can multiply by 10 to give us how we would need in 400 litres of water: 1g x 10 = 10g and then add add on the amount we would need for the extra 50 litres, = 1.25g (40 x 1.25)

Chempak total iron is 2%. I understand everything in the posts before the line in RED and after it. What I can't get my head around is why is 20,000 divided by 100 and if that's correct why is 20,000/100 = 20 and not 200 ??? I just want to understand what I am doing before I dose the Chempak.Question 2 - relates to the UKAPS nutrient calculator. I am about to restart using my APF dry salts. The APF recommended mix in 500ml water is 4 tsp KNO3 + 1 tsp KH2PO4 which I have used in the past. But when I use the calculator it recommends in 500ml water 3TBLS + 1 tsp+1/2tsp+1/4tsp+1/32tsp KNO3 and 1tsp+1/8tsp+1/64tsp of KH2PO4. While the amount of KH2PO4 is very similar the amount of KNO3 is higher by about a factor of 3. Is there a simple explanation for this? Given mine is 280 and I'm using the same fertz - I need a total of 7g (280l / 40 litres=7g) to give me 0.5 ppm. How do I work that out for my 1 litre all in one mix which adds 50 ml as an overall dose? Question 1 - relates to a post in January this year on Help with all-in-one recipe, on how much Chempak sequestered iron to add to a tank. The link is: