The Ecosavr solar fish saves money by preventing heat loss using a special liquid that sits on the surface of the pool. It virtually eliminates evaporation, which is primary way pools lose heat. This unique liquid is odorless, tasteless, non-toxic and 100% biodegradable so it’s safe for every pool and everyone. Just cut the top of the fish at the dotted line to activate the special dispensing design that will be effective for 1 month. Best of all, you won’t need to measure and add anything weekly, all you do is drop the fish in the pool and forget about it. For the best results, use 2 fish at a time in in-ground pools and 1 fish in above ground pools. Each fish lasts about a month. We recommend using this product in the spring, fall, or anytime nighttime temperatures are cooler. This is when you pool loses the most heat!