Depending on your water conditions, you may or may not need the magnesium sulfate. In EI, there is a remineralizer consisting of magnesium, potassium and calcium sulfates that is added once a week, again, depending on your water conditions.
EI was originally designed to be easy to follow, without a need for a scale. However, if you want, you can always use a scale. I believe Tom Barr has an article outlining the weights. If you want to use measuring spoons, it is assumed that each chemical is a level spoonful, and not packed down.
The main difference between EI and PPS-Pro is that EI relies on an excess of nutrients in the water column, which is prevented from accumulating to dangerous levels through the 50% weekly water changes. PPS-Pro relies on a 'just enough' principle, where you only dose what is needed.
EI was originally designed to be easy to follow, without a need for a scale. However, if you want, you can always use a scale. I believe Tom Barr has an article outlining the weights. If you want to use measuring spoons, it is assumed that each chemical is a level spoonful, and not packed down.
The main difference between EI and PPS-Pro is that EI relies on an excess of nutrients in the water column, which is prevented from accumulating to dangerous levels through the 50% weekly water changes. PPS-Pro relies on a 'just enough' principle, where you only dose what is needed.