Classical music doesn't increase plant growth, the studies trying to show it were dubious and sensational in their time and it did not stand up to scientific scrutiny.
Picking out a specific frequency is even more baffling to me, especially when you consider that so much of the content of even a single instrument playing a single note is the overtones rather than the fundamental itself, and even if an instrument or an orchestra tunes to a 432Hz A, they're always playing other notes and in other octaves even when playing a piece with tons of As.
There is no evidence tones of a specific frequency stimulate growth of plants, animals, or much of anything (unless it's a standing wave in an object at resonance, I guess), and if there was, wouldn't every greenhouse and coral farm be doing it already?
Also, the amount of noise generated by normal aquarium equipment almost completely drowns out external noise shy of yelling or tapping on the glass. Yes, I've recorded this to see.
But hey, the arguments made for it aren't scientific, they're anecdotal, so I'll fight fire with fire: I'm a classical musician who practices daily about 2.5m from my aquarium, for the first year or so the coral was very slow to grow, in no small part to inadequate light (a single XR15 over an e170 isn't great for anything that needs moderate to high light and isn't top center), and in more recent time, it's been reasonably happy and grows at a normal rate. Nothing exceptional about growth, survival rates, coloration, spawning activity, polyp extension, alkalinity consumption, etc.
