A thermometer is a definite necessity in order to keep your pond at the right temperature, especially for ponds containing fish and aquatic plants. There are different types. You can get a sinking or floating thermometer that will help you to measure the water temperature at different levels. The pond thermometer must always sit in the water completely, about half way down the depth of the water. Pond thermometers usually come with a hole or ring in one end attached to a thin rope or string so that thermometer can be left in the water and it will be easy to reel in and check the current temperature of the pond.
