I am getting a 48x18x22 terrarium. What size UVB bulb will I need. I will be going with T5 12% model from Arcadia. Do I need the 46 inch model or something less. Don't want to over expose.
I use a 36" fixture (with 34" bulb) in my 48x24x24. This let's one end be uv free. You may be able to get away with 24" as well. I would just make sure you have the basking spot covered.
I agree. The 22'' should be totally fine and provide the basking area with plenty of UVB but the 36'' would work too if you keep it to the front or back of the tank and off to the basking side. You want to leave areas with little to no UVB so I wouldn't use one larger than 36''.