Well... I'm 3/4 winterized.
The fish tank and in ground sump tank is wrapped with R-30 Insulation, and the 2 growbeds have been "greenhoused" (with a 15' x 4' piece of solar pool cover and a 9'x10' plastic visqueen removable "top". 2- bent 1/2" conduits per growbed form the frames to hold up the "top". Top is secured to conduits by black 1" binder clips. I put $5 moving blanket over the top at night when temps are to get below 50 degrees.
Last night was trial nite....temps got down to 43 and I flowed water thru the 2 growbeds all nite and water temp was maintained at 62-63 degrees with only the 1- 90 watt light bulb underneath each growbed (the light bulbs are thermostatically controlled to come on when the temp under the growbeds hits 52 degrees).
I estimate the cost of the light bulbs being on for 10 hours is .20 cents a night. I have a 1700w DIY heater in my sump tank... but it didn't kick on last night at all. (I have a meter on it so I can watch power usage and cost.)
The reason I "greenhoused" the growbeds is that I found that a cannister filter wasn't processing the fish tank ammonia very well at all...so I decided to get water flowing to growbeds again as the gravel kept the water beautiful before I shut the flow off for the winter.
Since I wrapped the growbeds to keep water warm and clean for the fish...I figure I might as well grow winter crops in them...so that's what I'm going to do now. Spinach, kale, beets, etc... here I come.
I'll have to wait and see how it works when the temps get down to 30s. But for now.... this was a very sucessful attempt to accomplish what I needed- better filtration for the water. (I only have 2-8" koi in the fish tank but they can really foul the water if you don't watch it.)
I'll have to open the "tops" during the midday time of course, or the plants will heat up a little too well...just like the greenhouse.
Hope this helps anyone needing to solve the same problems that I had.