Advice on pool/tank

[keith_r]

yup, remove the heater.. copper will not be good with the fish, but the spa will make a nice tank..
use the ibc cut in half for deep growbeds, i've seen IBC 's cut lengthwise as well..
i've read up on a few of the "kit" sellers in the US, and the systems i've seen would work, but not anywhere near the volume of fish and plants they promote.. and the biggest failure point i've seen on systems has been from overstocking...
but i'd really like to get some "nice" growbeds (i like byap's gb's)

[foodchain]

I don't know what type of hot tub you have. Mine is full of copper at nearly every fitting underneath. Not exposed from top. I first looked at mine with the same idea. Then tabled it when I looked at the complications. You may be able to use like a heat exchanger though.
Coil copius amounts of tubing in the main pool. Use pool to heat water like normal, then pump tank water through the tubing slowly. The pool water will heat the tubing, and in turn the tank water without actually coming in contact with it. I do something similar with my attic here in TX with PEX lines. Works very well, and is free as I use city water pressure to push it up, then use gravity to bring it down to mix with cooler water as needed for the ideal temps.

[commander]

I have been in and under this tub checking it out. I am pretty sure if I take out the heater loop, everything else is PVC. I like the idea of a heat exchanger. Where in TX are you. I am up in Lubbock. I have considered coiling ABS plastic pipe (black) on the roof of my shop which faces South and using that as a really crude solar water heater. The idea of the TREX pipe sounds good.