Backyard Aquaponics
A place to discuss aquaponics

I believe our mean annual temp here is between 75 and 80F (23 -27C) and that is usually considered to be the ground temp at about 4' (1.2 M) of depth.

sounds like concrete would b fine
and a good regular temp.
hang on is that -23 or - 23?

The lowest temp recorded here that I know of is 27F (-2C) which lasted about 1 hour, and by the end of the day it was back up to 40F (4 C). The ground never freezes, and I have never measured my swimming pool water (inground concrete) below 64F (18C), even in the coldest time of winter.

My fish still live in the sump. Every time I price the above-ground plastic tanks, looking at those over 600 or 700 gallons, I keep coming back to the ferrocement fish tank as a cost-effective extra-large option.
Plus you could shape the outside to look really cool: