Buy dry powders from aqua essentials.
Potassium Nitrate - 40g to 500ml of water and adding 10ml per 100L of water would give you a value of 5ppm.
Potassium Phosphate - 15g to 500ml of water and adding 5ml per 100L of water would give you a value of 1ppm.
Potassium Sulphate - 55g to 500ml of water and adding 10ml per 100L of water would give you a value of 5ppm
Magnesium Sulphate - 70g to 500ml of water and add 50ml once a week per 100L of water - this would give a target of 7ppm.
Trace mix - 15g to 250ml of water will give you about the same concentration as off the shelf products. It is also a good idea, if you can, to add 0.5ml Normal hydrochloric acid as this helps to prevent the chelator from breaking down.
You can mix these powders in water.
ONly the ones highlighted in bold are necassary. Any others are optional.