A couple years ago I learned that the Bosnian community have long raised goldfish as "Ramadan" fish, due to their golden color -- they would serve that form of carp during Ramadan holiday meals. I'm in zone 4 and the Bosian elder I visited had set up a pond outside & a massive double filtration system in an indoor tank, for winter periods. He said the goal was to raise the goldfish to frying pan size, then harvest. He was able thus to buy simple comet goldfish from pet stores at only a few cents.
Having raised goldfish as aquarium pets, I knew the growth rate if they are given adequate space. So I can see how this would be a great choice as a meat fish. He spoke about his bafflement that Americans are so unwilling to eat goldfish, pointing out they are "merely gold colored carp". I explained that in many parts of this country carp and catfish of any kind are assumed to be "trash fish". Stupid on the part of the Americans really. We eat Pork and it eats pretty nasty things if given the opportunity & so do chickens... so why the attitude toward carp?
My husband was raised along the Mississippi and there catfish is eaten. I was raised in Colorado where catfish are seen as a "trash fish". So clearly each region has created its own taboos. I for one am working toward developing myself a Ramadan Pond in my garden. Instead of bringing the fish into the house in winter, I plan on using an old ranching technique & have a water-tank heater keep my 100 gallon livestock tank ice free.
Wondering if anyone in my zone has been raising carp, other than for the European export market?
I remember seeing a system where the fish areas were inserted into the soil in a green house. The water acted like a heat sink for the green house.
If you could put your barrels in the ground and put a hoop house above them you can add solar water heaters like system to heat barrels of water to add additional heat .
If you tap into the heated water at night you can likely maintain water temp in the ground barrels. You could have crops above and fish below. Fish do not need a lot of light.
Being a smart alec beats the alternative. This tiny ad knows what I'm talking about: