Wow. My water temp was a miserable 91 Thursday night around 10 PM. Today, my water temp was a wonderful 82. Now, we did get a storm yesterday, but my water never cools this fast with just rain. I say if your water is too hot you definitely need to buy these, or be creative like Dave and fabricate them yourself. Now that I see them and see what they are in person, they don't look like they would be that hard to make yourself. It does work!