Thanks so much for your reply. After reading you response, we did in fact attempt to contact a local university. We are awaiting a reply. As for feeding the fish - Rainbow trout still eat at colder temperatures. Unlike koi or goldfish, they remain active although less so. They are cold water fish and will continue to eat all year. The trout are active beneath the ice and in fact, will accept offerings from ice-fisherman throughout the winter on our local lakes. As stated earlier, the fish had been feeding (re stomach contents) on natural aquatic insects thriving in the pond. We had continued to feed them pellets as we were not sure if there was enough natural food to sustain them throughout the winter. The trout farm where we buy or fish, feed their stock throughout the winter but just not as much.

Hi there. I am in z 6a according to the new USDA zone maps... in western Mass. First, i want to ensure you that you certainly can GROW crops 4 seasons. I just harvested beets that i sowed in november. I have been eating lettuce and spinnach all winter and just picked raddishes that i sowed in late january. So don't think you are limited to using the GH as a big cold storage cellar. I looked at a few designs before starting mine. I looked at the sunny john design which has plennums running beneath the surface to heat up the soil. I rejected that as too expensive and too much work. There are studies that show moderate success with that. I looked at excavating the soil and replacing with stone and circulating the air through the stones. Again, while it has some benefits, i would need power and the stone would be expensive. I went with the solaroof design which is a double greenhouse that uses soap bubbles as an insulator at night. I never got that far as i still haven't run power out to the GH. So i just have a double walled gh, with 2 foot minimum airspace. My specs: GH interior 48 x 22 GH exterior 52' x 26' GH height interior 11' GH height exterior 14' Both were built with commercial grade greenhouse tubing. If i were to do it again i would save $$ by framing the interior with something cheaper. Heating: None Ventillation: 8 foot wide x 2 foot high gable ends vent. The vents are at the peak of the gh to allow heat to more easily exit. I also have an 8 foot wide door on one end. I will likely add a door on the other end to aid in cross ventillation. I never added the bubbles. I would like to so i could determine if i get additional zona protection. Some of the more interesting "successes". I grow tomatoes into december. I grow all sorts of cool weather crops: peas, beets spinnach, lettuce, raddishes, chard, green onions, dill, thyme, rosmary throughout the winter. Some i actually re-sow midwinter. I "overwintered" citrus, which died back but sent out new shoots. potatoes keep trying to grow but die back with each "Freeze". They are now growing in ernest. I put "freeze" in quotes as i am not sure of the interior temps. Outside temps reached -14F last year and i still did not have ice in the GH. I used to get ice, but i built a water tank that holds 1500 gallons and have not had frost or ice in the GH since. I have fish in the tank. I have not read the winter garden book you have. I have done none of the calculations regarding thermal masses. I can't tell you whether row covers are better than a second GH layer, but if the book says you can't GROW crops but can only overwinter them, then based on my experience, row covers don't do the job as well. I do not have below the ground insulation. I grow my crops directly in the soil. Ask away...

NG - I just read this post for the first time today. See if any of this fits: When plants are in leaf, cold soil temperatures can make phosphorous (P) unavailable. A lack of P causes a build-up of a red/purple/maroon pigment (anthocyanin), so it's very possible that is what you were seeing. Did it straighten out later in the growth cycle (all the new leaves) after it warmed up? Another physiological issue can be related to something different. A P deficiency is not the only suspect cause of purple leaves. Nearly any environmental condition that puts the brakes on growth and the accompanying use of sugars, but does not limit sugar production (photosynthesis) can cause anthocyanin buildup and purple leaves. (tight roots?) If it's nutrient related, you might get a hint by noting if only the outer edges of the leaves are purple, in which case it may be a K or Mg deficiency. If the center of the leaves are also purple, it could be too much Ca in the soil or irrigation water blocking uptake of P (see deficiency symptoms above) and Mg. Al

I just have a small preformed pond (Sam's Club) probably not more than 150 gallons...I got most of my info from the pond forum...have had just plain old goldfish that have survived three winters here with just an airstone going...you many need however to pour a cup of hot water on it when the pond freezes solid...lurk and surf on the pond forum they have a wealth of info.