So you just pour a bit back in at a time as the temp rises to bring it down to normal?
Sounds like that should work. You must have a big tank if you can still run it with 9 gallons missing
Interesting.
On the issue of the cooler though, bottom line I think you need to eliminate as many of the air interfaces and plastic pipe interfaces as possible. Air is pretty inefficient in heat transfer as is the plastic.
Sage