Every species of reptile will have its own set of specific humidity requirements, with some reptiles requiring little-to-no humidity and others requiring up to 80% humidity over a 24hr period. Semiaquatic reptiles, reptiles whose natural environment is in and near water, will need to be able to fully to submerge themselves with room to swim. For many semiaquatic species, the bulk of their daily activities, such as feeding, social interaction and reproduction occur under water. 

Should your enclosure require a moderate to large body of water, aerating and filtering the water helps to reduce build up of organic waste and disease-causing bacteria. Fresh water species will always require some kind of filtration device as still, fresh water in a warm environment will go bad, fast. For saltwater species, the salinity or level of salt in the water, should be regularly monitored to ensure it remains stable. Knowing the exact pH or acid level, will help to dial in the kind of water you will need to provide. 

Fresh water should be made available every day in order to prevent dehydration. Most species will readily drink from a water bowl, but a number of reptiles such as Tree Boas, Green Tree Pythons. Anoles and True Chameleons consume most of their fluids by lapping water droplets that accumulate on their scales and surrounding foliage. The use of an automated misting system or a daily spraying regimen will ensure your reptiles are receiving adequate water, in addition to increasing relative humidity throughout the enclose. 

The main goal with humidity is to best mimic the natural environment of your specific reptile. Without adequate humidity, your reptile will be susceptible to dry skin and abnormal skin shedding, especially in sub-tropical to tropical species. Excessively high humidity can result in skin infections in some species ad the use of a hygrometer is highly recommended.

Check the chart under General Husbandry to confirm your reptiles desired humidity range.