I think using "old" aquarium water is great for growing green, healthy Orchids. ( I used to do an at least 25% water change once a week, siphoning out the detritus from the gravel into a bucket.) I still would add some Phosphorus in the form of NPK fertilizer/higher middle number once in a blue moon. Just to encourage the next blooms.
May I ask, what kind of Orchid did you receive?
