Thanks Hoppy -- I've got the dry fertilizers on order, should be here early next week. That sounds pretty close to what Nilocg prescribed to me:
1/4 tsp KNO3 3x a week
1/16 tsp KH2PO4 3x a week
1/16 tsp K2SO4 3x a week
1/16 tsp CSM+B 3x a week
Dose CSM+B MWF and the other three 3x per week on opposite days as the CSM+B. On the 7th day do a 50% water change and afterwards add 1/2tsp of GH booster.
You say my tank at ~20" substrate-to-light with a single Ray2 would be considered low-medium light; I have read that HC requires high light -- do you think I should consider an additional light source, or would my single Ray2 be adequate with proper CO2, EI dosage, and Excel dosage?