Hello Osymandius (wow that's a keyboard full) and welcome to Pond Boss.

Ahh the age old question, to solar or not to solar. Depends (in my untrained, uneducated, unsolicited opinion) on several things. DC air pumps won't develop any where near enough flow at enough pressure to deliver air at much of a depth.

How big is your pond in terms of both surface area and depth?

What is the basic shape of your pond?

You can run air lines fairly far (I believe up to 1,000 feet or so) so you might be able to have the pump near the power source and just run the air lines the 300 feet fo the pond. The advantage of this is that you can then get a good pump and not worry about running power lines (just air lines).

Getting enough solar equipment (panels, batteries, wiring, charge controller, inverter, etc, etc) to power a decent AC pump using solar is EXPENSIVE.

Anyway, get us some info on the pond size and depth and I'm sure on of the experts will give you some feedback.

JHAP
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"My mind is a raging torrent, flooded with rivulets of thought cascading into a waterfall of creative alternatives."
...Hedley Lamarr (that's Hedley not Hedy)