[Zapins]

1 lb of mono potassium phosphate lasts 15+ years, 1 lb of KNO3 will likely last 2-3 years, 1 lb of CSM+B probably 5-10 years.

You'll also need K2SO4 which I don't believe that site sells.

Excel is not a direct substitute for CO2 gas. For the fastest and thickest growth you'll need pressurized CO2.

You can dump the measured dose of dry chemical into your tank.

 

[Zapins]

Calculate the doses out for yourself. I use 0.8 grams of phosphate once or twice a week in my 90g tank, 1 gram of CSM+B per week, 12 grams K2SO4, and 10g KNO3. You'll use about half that depending on your dose. I forget how many grams there are in a pound (400ish) so calculate that out in terms of weeks and you'll have your answer.

 

[Zapins]

A separate packet of iron would be a good idea, you don't want to add high doses of CSM+B to your tank just to add iron. A good iron supplement is DPTA chelated iron.

You'd have to check the details on the package you are ordering, I'm sure they sell several different packages.