Don't believe those bad reviews! I've used these little guys for a long time now. They just float around in the filter compartment of my spa and do their job just fine. my husband and I live in the mountains and use my spa daily. Admittedly, we don't shower before we get in every night so we really keep an eye on our test strips. These seem to last about 2 months or so before they start looking icky then I just toss one and replace. Anyone who says they don't work must have thought that the starfish was going to be responsible for testing and maintaining the necessary chemicals on a bi-weekly basis. Hmmmm..... Thanks Staff at Leslies! I love mine!!