Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Figure out what is the total amount you want to give the tank for a couple of weeks.
Keep the phosphate fertilizer separate from any iron fertilizer (trace minerals often include iron, and certainly chelated iron ferts are iron). As burr says: one blend can be N-P-K, the other would be traces, including iron.
Put the right amount of each into 2 bottles and add enough water to dissolve the ferts.