What Wattage bulb do i need for my vivarium?

Making sure you have the correct wattage bulb in your enclosure is an important part of setting up your reptile enclosure. 

Unfortunately there is no magic formula in that X size of vivarium requires Y wattage heat lamp.. too many other factors come into play such as ambient room temperature, insulating properties of the enclosure and most importantly the enviromental needs of the species in question. 

You need to aim for the lowest wattage possible that will achieve the desired basking temperature for your species. When using a basking light with a thermostat such as the Microclimate B1 dimming thermostat, If the bulb wattage is too high the thermostat will turn the bulb down to maintain the correct temperature and this means the bulb will be hardly illuminated which isn't ideal for species that like a nice bright basking area. Also using an overpowered bulb in a vivarium also means in the event of a thermostat failure however unlikely then the vivarium would become dangerously overheated.

If you have a thermostat that displays the power output being supplied to the heater such as the Microclimate Prime 1 or 2 thermostats, aim for a power output of around 90 - 95% to achieve the basking temperature. This allows a "reserve" of about 5 - 10% power that the thermostat can use if the ambient room temperature drops and it needs to increase the power output. 

usefull Links

Basking lights - http://www.livefoodsbypost.co.uk/basking-lights-727-c.asp

Thermostats - http://www.livefoodsbypost.co.uk/vivarium-reptile-thermostats-330-c.asp