My friend made a DIY chiller of the same design with a large circular beverage cooler. Wound the tubing all the way around the interior walls, with fittings for the intake, powerhead tube back to the tank, etc. He would fill it with ice and could cool the temperature for a 180 gallon tank about two or three degrees in about 20 minutes. As I recall, it was a google search for DIY chillers that gave us the idea.