"JG" wrote in message om...
I thought about buying a piece of titanium tubing (can buy a 3' length
for $40 or so) and bending it into a coil.
Then pump water through it and blow a fan across the coil.

What tubing diameter you are thinking about?
If you never worked with titanium before
you should be aware, that bending thick pipes
made of it is not an easy task to do...

Would this have any affect, or is the coil too small?

I have similar problem with my 30gallons reef - need to lower
down the temp only a couple degrees - I run a coil of compression
tubing (polypropylene or something similar, milky colour) and
use cold tap water to drip through it. Make some experiments
with it, if the tap water is not expensive in your area and using
it for cooling is not forbidden you could achieve this 4 degree
target doing the same.