Refrigerated Circulation Bath

I have just aquired a Refrigerated circulation bath from work (it was being thrown away).
This baby is designed for cooling lab instruments, and can maintain temps down to -20, and has a built in pump.
I just wondered if there were any problems with taking things this cold (comp does not run all time so i'm worried about the cpu getting damaged cooling then warming a lot)

Also does anyone know what sort of antifreeze i should use.

All help is appreciated, as this is my 1st attemt at water cooling.

Should be fine provided the insulation is really thick. From my own experience I would suggest at least 1" (25mm) thick and remember to do the underneath. I only switch my pump on while working.
You'll need about 40% antifreeze and then you will have to see how you go. I am using ethylene glycol based stuff.

use the green kind of antifreez, make sure it has that gly... stufff i dunno how to spell it..
and ull have to insulate your mobo from condenstsion, cuz giving the WB -20 will give alot of condenstsion depeneding on room temp