I will not make this post any longer than necessary by adding information about aquaponics. If you are not interested I do not want to waste your time reading a longer post than necessary. If you are interested but do not know about aquaponics then you can Google.
As an experiment I set up a 100 gallons fish tank in late summer with two growbeds alongside and at a slightly higher level. I pump from the tank to the growbeds on a 15mins to the hour basis. I made a bell siphon to drain the beds back to the tank. It works brilliantly. The beds have a few overwintering plants in them, but my idea is to grow summer veg and save on water (which is recycled and not lost as in a ground garden) if the experiment is successful. Time and water shortage are a problem when my olive and almond trees need so much water and attention. I will be making an irrigation pond next Spring and intend to use this for fish, so could set up growbeds for that on a much bigger scale, or use floating growbeds. Almost all of the irrigation area drains back into where I will be making the pond so any leaching of nutrients through the drainage of water back to the ponds will also be recycled.
In my experiment I have the tank set behind a low wall that forms the entrance to an otherwise open, but roofed, area prior to entering the wine cellar. This wall protects the tank from exposure to the sun in the summer when the water would be overheated, but is ideally situated to catch the winter sun. Obviously this leads to thoughts of using solar gain to slightly raise the winter temperature of the fish tank through a warming (not heating) coil in the tank. This would keep the fish active, feeding and growing instead of just marking time for a few months.
Anybody have experience of doing this, or thoughts on how best to proceed? What area of collector do you suggest? I can fit the height/width to suit. Temps rarely drop to freezing point. I would not make any allowance for cloudy days, the water temperature would reduce naturally, and that is acceptable. Pex is unobtainable locally and I do not want to go to the cost and hassle of copper. I am willing to chance some irrigation pipe – this might influence suggestions for the size of collector. It is a small scale experiment and I want to keep costs to a minimum.