Solar-powered pond equipment sounds great, but in my experience that is as far as it goes.
Anything solar-powered needs to have the solar panel at the "optimal direction/angle" that will not be easy being on a balcony. 😕 Then you have the problem of "not enough sunshine" to power your solar device, not just in the summer but in winter the sun is never that bright, and of course there is night time when there is no sunshine at all, so anything solar will not work.
There is also the problem of freezing, being outside on a balcony.
I would never suggest anything solar for a pond, let alone a balcony, as there is never enough sunlight, and to make it work you need lots of equipment, that in turn makes it financially not viable. 🙁 Not in this country