The history on this comment is that I upgraded my 30gal with a MH
light. Immediately, I began to have temperature problems. There was so much light that it began to raise my temperature too much by the end of the day.
So I ordered the "Ice Probe". It was small, and relatively cheap compared to other chillers.
Then I added a 10gal sump. Since then the water temperature has been very stable...but it was winter.
It has been getting pretty warm here lately and my temperature has started to climb again. So I finally dropped the Ice Probe into the system.
Here's my point. I'm impressed. This thing works extremely well. I was concerned that it wasn't big enough to influence 40gal, but it handles it without problem.
I took the easy way on installation. It is designed to bulkhead directly through the wall of a tank, but I just hung it in the overflow of my skimmer. Here's a picture of the chiller in action.