Regular exposure to ultraviolet light is essential for a tortoise to receive vitamin D3 (Hermans, Horsfieldi, Leopards etc). The ultraviolet light is provided using a UV fluorescent light tube in the vivarium. This is placed not more than 12" to 18" from the tortoises rest area, and should be replaced every 9 to 12 months. For dayime heating and lighting, a 60 or 100 watt reptile heat bulb should be used. The daytime temperature should be around 80 - 85 deg F at the heat source, and should be no lower than 75 deg F at the un-heated end of the vivarium. The night time temperture should not drop below 65 deg F.