Mercury lamps was specially developed for large terrariums and reptilian species which require a large amount of UV-A and UV-B rays. Many reptiles requires UV-B rays in order to be able to synthessise Vitamin D3. Mercury lamps can also be utilized for treatment of metabolic bone diseases as well as calcium deficiency. The state of health of the animals suffering from these illnesses often improves within a short period, insofar as regular radiation with mercury lamps has been implemented.