OK, I thought that this might be the case. You are probably going to want to buy some dry ferts online which wind up being much cheaper than liquid ferts of the same kind. The Flourish (comprehensive?) is good for your micro nutrients, but you might also want to get some Iron as well (to be dosed on the same days).
You will also want to buy the dry ferts I was talking about. Since you are running a high tech tank with high light, you are going to need to dose NPK (nitrates, phosphates, and potassium) into the water column. Read the following thread as it has some very useful information about dosing regimes:
I dose macros 3 days a week, micros the opposite 3 days from macros, and one day of rest (no ferts) the day before I do a %50 water change. This whole process is centered around the Estimative Index (EI) method.
Here are the links to where you can buy the ferts:
Personally, I would buy:
2lbs of Potassium Nitrate (KNO3) for N
2lbs of Potassium Sulfate (K2SO4) for K
1lb of Mono Potassium Phosphate (KH2PO4) for dosing P