Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Dosing will depend on your tank.
High light, CO2... dose more (more often or higher dose or both)
Moderate light, Excel or DIY CO2... not quite so much.
Low light, no CO2... may not need full dosing.
I do not recommend a blended product. How do you know your tank will use those nutrients in those ratios?
Example: Some tanks (usually low light) will test enough NO3 from fish food that you do not want to dose more (such as KNO3). But these tanks often lack potassium and iron. If your tank is like this how will you separate out the K2SO4 to use it, and avoid the KNO3?
Do not use Epsom salt without also using calcium unless you know you need magnesium but not calcium.
Plants use calcium and magnesium in a ratio of about 4 parts Ca: 1 part Mg.
The ratio in the water does not have to be exactly that.
If your GH test shows at least 3 German degrees of hardness then you should be OK as far as Ca and Mg go. If you want harder water for certain fish then use a complete GH booster with Ca and Mg in the right ratio.