If you are going to go heaviy planted with some fast growers like Hygros, elodea, hornwort, Wisteria or others then I would suggest getting all of them. KNO3, KH2PO4, K2SO4, MgSO4, CaCL2 and CSM+B (CSM+B is your micro or trace fertilizer). These can all be obtained from HERE
. I would suggest the following ratio:
3 K2SO4 (you will go through it much faster)
I would suggest getting 2 pounds of each and 6 of the K2SO4 due to the levels of dosing you could be doing. But this depends on your planting density of course.
Yu might even want to get the Barr's GH booster which will eliminate the need to get both Mg and Ca because it has both. Getting them seperate will allow you to control the dosing a little more. I would get them seperately, personally.
Remember to make sure you always have a KH of at least 3 which can easily be controlled by adding Crushed coral in small amounts and checking your KH a couple days later. Keep an eye in it and if it starts dropping add a little more to keep it steady. Calcium Carbonate can be used for the same thing but you need to adjust your water when you do a water change. Also keep your GH steady at about 5-6dKH because this can be even more stressful than small ph Swings with a normal KH.