I always thought that one of the most sensitive creatures to chemicals were frogs. I always hear that dead frogs or no frogs is the tell tale sign of a chemical problem in the environment. So why is it that I always have frogs in my pool. They love to hang out in the skimmer as lots of bugs are sucked in there. It is sort like a drive up window for them. The frogs are usually small, and I have had some that have been with us for a month or more at a time before the vansih. Right now I have just one, but he is HUGE. He is about the size of three tennis balls in a row - big Rear frog.