Hi, The Rotala Butterfly calculator doesn't have the Chempak Sequestered Iron ( with Magnesium and Manganese ), it has DTPA 10%,11% and 8% but the one I've got says it DTPA 1.2% and it has options for EDDHA Fe 6% but I have 0.8% ? It says it's total iron soluble in water is 2.0% on the box. The warning on the box says says it contains Manganese Sulphate which is "harmful to aquatic life" so I'm getting nervous as I have fish in there. I tried to read the other thread but I found it overwhelming, I'm an artist I haven't done "science" for 27 years. If it didn't have discus fish in it I could experiment more but I don't want to kill anything. It says in the thread - "You know how much iron (in ppm = mg/L) you've added from the percentage of iron in the compound (6% for FeEDDHA), how many grams you've added and the volume of the aquarium. You can use one of the <"online calculators">, if you aren't confident about your calculations." So I think if I put 1 gram per litre of Chempak in the water I will end up with 120ug of DPTA and 80ug of EDDHA in each litre of water in the tank? In the thread FishWorks writes about aiming for !ppm of Fe DPTA, I presume I should put 10 grams of Chempak per litre then, seems a hell of a lot? Also do I ignore the EDDHA? I'm baffled! What I have learnt is that I've been dosing my chelated trace hugely ineffectively because I found that if I kept my ferts in a cupboard I would forget to put them in so I've been storing them in almost direct sunlight for donkies. Because it didn't say in the instructions I had to keep them out of the light I assumed this was ok, but if it becomes unavailable to the plants in 30 mins of contact with light (in the tank) then my stuff has been unavailable way before it gets in the tank. I'm not quite sure how I managed to grow anything!