The Aquatop Floating Glass Thermometer gives you the ability to easily monitor the water temperature in your aquarium. The thermometer is easy to read and has a safe temperature range display which provides the recommend temperature parameters for most tropical fish. The Aquatop Floating Glass Thermometer includes a suction cup mount which securely attaches to any flat glass or acrylic aquarium surface. Plus, the thermometer will float if knocked loose by fish, snails or during routine maintenance. Safe for Fresh or Saltwater use.