I have seen people growing their Phal in full water culture (water level reaching 1/4th of roots) using JUST rainwater, no fertilizer, nothing! just top up the rainwater when it gets low. and their phal still keeps on blooming and producing new spikes and 3 keikis and all healthy for a whole year!
Where do the nutrients come from? Is just rainwater enough? Is using fertilizer actually redundant?