One can refine fertilization, but in general, here's a very simple approach. Use any balanced orchid fertilizer (like 20-20-20)... doesn't matter the exact number, but rather that all are the same. Use 1/4 to 1/2 whatever it says on the bottle. (if it says 1 teaspoon per gallon, use 1/4 to 1/2 teaspoon) Then perhaps once every week or two weeks ("Once weekly weakly") If you want to mimic what orchids get in nature, cut the concentration even more and fertilize with every watering, flushing with clear water at least every 4th watering. Personally, I use the "every week or two" regimen, really easy to keep track of and to accomplish. When in doubt, use less... if a plant gets less than the optimum amount of fertilizer, it may grow more slowly and/or produce fewer flowers. Too much, on the other hand, can kill it. Think of fertilizer as "vitamins" rather than "food".