I specialize in blue tilapia.  I originally got into raising fish as a way to provide a high-protein diet for my Dad (who is type 2 diabetic), and I chose blue tilapia for several reasons:

1) they're primarily vegetarian and feed heavily on algae, which allows me to grow their feed on-site and basically convert algae/veggies/etc into lean healthy protein for my Dad;

2) they grow really fast (some people call them aquatic chicken);

3) they're mouth brooders (i.e. females hold the fertilized eggs and newly hatched young in their mouths), which is fun and makes breeding them easy;

4) they're really robust and tolerant of poor water conditions (helpful for beginners);

5) they're the most cold hardy tilapia--other varieties of tilapia die off in the mid-50's, blues die off in the upper 40's;

The down side is that since they're tropical fish, they die off in the upper 40's and grow 3 times slower at 72F than at 85F, so managing water temps is very important.

What I read was about tilapia and I remember thinking that the temp. requirements would be difficult. I think I also read that catfish could be raised at a cooler temp. What are you useing for tanks? I had thought about stock tanks like for watering live stock but I think they are pretty expensive. (Thanks for all the info....)

One of my fathers greenhouses had a "basement" where he had put plastic barrels full of water.
There was a blower that sucked the hot air from the top of the green house when it got hot due to the sun and blew it down onto the barrels to warm them up.
At night the barrels released their heat when it was cold.

RichinNJ - great idea!

James - I really like the idea of using above ground pools. So much to think about...

This is really interesting. The price tag on the "greenhouse in the snow" greenhouse I was looking at was around $17,000, but that included a manufactured frame, lots of corrugated tubing, and very nice covering (designed to last for 20+ years). I think it was 17'x96'.

I think a less complex structure would be a lot less expensive and perhaps just as good. It's really interesting to me that you're only going down 3' but are getting such a great moderation in temperatures. We rarely get below zero here and I'd be interested in a structure that stayed above freezing (for citrus growing). Does it also stay cooler in the summer or do you vent it or take off the plastic?

Just thinking out loud here, but having a "backup" of some buried tubing with a fan attached might be nice as it'd serve to heat in the winter and cool in the summer (making it okay if I would forget to vent the thing).

Thanks for the replies. Did you dig everything by hand? If so, my hat goes off to you! I am considering a small tractor with a backhoe attachment that would hopefully make digging a lot easier. Sounds like some sort of cooling system (mist or otherwise) would be a good idea if the extra cost is feasible. I'm thinking it'd cost anywhere from a few hundred to $1k for the tubing plus fan.

Neat stuff. I'm following this topic so I'll be interested to see how it ends up for you.

I dug the original aquaponics tunnel, the garden pond, and the first pit greenhouse entirely by hand.  For the new pit in this thread, I did the first 1/4 with a Bobcat and the last 3/4 by hand; now I've decided to widen it, though, so by the time that's done it'll be more like 1/5 via Bobcat and 4/5 by hand.  I'm pretty sure at this point that I never want to dig another one by hand again :)

I agree that it's a good idea to incorporate in some sort of climate control system.  I like the buried culvert method: it's fairly easy, low cost, and would help to warm the root zone if you buried the pipe underneath the planting area.  Pumping large volumes of air into my water, rather than through underground culvert piping, produces a similar effect in my aquaponics tunnel, but combining both methods would be better.

I was glad to discover that Fitch (the 'greenhouse in the snow' guy) and Stoilov (a guy doing something similar in Missouri) had employed the culvert method.  I had toyed with the idea in my own mind before encountering their systems, and it's nice to see that they've had success with that method.

Congratulations so far, James. It looks great, and a great idea, too. I've read about the walipinis, but this seems better/efficient. Thank you for the information and please continue to give us updates. I find your project fascinating.

Thanks, Bill :)