Backyard Aquaponics
A place to discuss aquaponics

Initially I was going to add 2 x 250w 12v mono panels to power my system but I started to think maybe I should ise 24v PV system in case I wanted to expand it and make use of it in my shed etc.

Any recommentations?

I went with 24V system because it matched my well pump. Now I have 24V inverters so I'll stick with 24V.
My system runs on 25 watts so there is no great power draw. One 250 watt panel is plenty at my current use.

You can generally use 2 X 12V panels in series to charge a 24V battery (via a regulator of course), assuming they are 72 cell panels. What is the Voc and Vmp on the panels?
In hot weather 60 cell panels may struggle to get some batteries to full charge if there is much load on the system.
24V will be more efficient than 12V- less heat loss in the cables, although if you are only using a very low power pump, that wont be significant. Alternatively, you can use larger diameter cables, at more expense.

If you are planning to expand, make sure your panels have reasonably standard output parameters, so that adding more panels keeps the same Vmp, Imp and Voc.

Gene, are you using 12 or 24 volt batteries?

I use 24v - it significantly reduce the thickness of wire required - thus reducing setup cost and energy lost

you'll find a lot of info on google if you do a search "24v vs 12v solar"

I use two 12V batteries wired in series.

We are using a 100w portable panels to a 120amp/hr deep cycle battery,
from there to a 300w inverter and onto the pump.
The pump is a 20w x 1000ltr/hr drawing 0.145amps/hr.
But for safety we run all the oxygenation from mains.
So far its been really good, no major issues,