Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Flourish Comprehensive contains iron, but perhaps not enough for some plants.
Over the last year or so I have seen several posts about over dosing traces (the main ingredient in Comprehensive). I would get the other 3-pack. Then you can slightly under dose Comprehensive (that is, all the traces) then make up for the low iron with the iron fertilizer.
Once you get used to dosing fertilizers you might decide that dry ferts are the way to go. When you buy any of the pre-mixed materials you are paying for shipping water with just a little active ingredient. When you buy just the active ingredient you add your own water. Much more cost effective.
Granted, a small tank would take a long time to use that much active ingredient, but most of us end up with more than one tank, and larger tanks as time goes on, so the cost for ferts could skyrocket if we did not switch over to dry.