No, you do not need a chiller; however, it is convenient. For occasional use, a 5-gallon circulating bucket shouldn’t have an appreciable rise in temperature to adversely affect the lifespan of the laser tube, and you can use ice packs to regulate the temperature. Beyond an hour of lasering, it becomes more an issue of practicality than anything else. Changing out ice packs takes freezer space, and, every time you open the lid of the 5-gallon bucket, you risk introducing contaminants and debris to your coolant. For more information on the benefits of a water chiller.