Just kidding, the dose depends on your tank size. The larger the tank the more expensive Seachem becomes and dry fertilizer (KNO3, KH2PO4, CSM+B) becomes a more attractive option. Start adding fertilizer right away, but Seachem Flourish is primarily a nutrient source for trace. Depending on what else you have going on (light, CO2, GH, etc.) you are going to need macronutrients as well. Fish and fish food can provide some nutrients, but you might want to add a GH booster like Equilibrium with your water change. Personaly, I find the directions with some Seachem products diffucult to understand. This link will take you to a nutrient calculator. http://www.fishfriend.com/fertfriend.html
Now, decide what your goals are, high tech/high light, low tech/low light, etc. Good luck.
Do I really need macronutrients? I googled online, and there's a post from seachem (http://www.thekrib.com/Plants/Fertilizer/flourish.html
) that says if we have fish then the small amounts of NPK in flourish should be enough. My tank is a 28Gallon, by the way.
Quoted from that post -
"Seachem supplies an NPK source in its Flourish, however the levels
we set in the product are meant to complement the other natural
sources (here I'm referring to P & N) of these elements. If you have
even a few fish in your planted tank they should provide sufficient
levels of nitrogen and phosphorous. One advantage with Flourish is
that the nitrogen source is in the form of amino acids which are
utilized as preferentially as ammonia is and even if the amino acids
are broken down by bacteria, it is broken down in to ammonia first
which can be utilized by the plants as well. The amount of these
constituents that we put in Flourish is enough to be of a benefit but
not so much that if you have a number of fish you are not going to be
adding an excess of N & P if you are using Flourish. If you have no
fish at all and no other non plant species, then the amount of N & P
in Flourish is probably not going to be sufficient (of course
depending on the number and size of your plants)... in this case a
good economical approach would be to either get a couple of
inexpensive fish or add a bit of an ammonia solution (IMHO).
Gregory Morin, Ph.D. ~~~~~~~Research Director~~~~~~~~~~~~~~
Seachem Laboratories, Inc. www.seachem.com