Thank you so much for the help!You should place it next to the heat lamp so the tortoise will benefit from the UV while basking. You should put it on a timer, about 4 hours a day is good. I would set it to be on when your tortoise usually basks. The only way to know for certain how far away the lamp should be is by using a solar meter. But referencing the arcadia lighting guide will give you an idea. With the T5 something in the 40 to 60 cm range will be good.
Medium UV Species - Arcadia Reptile
Medium UV Species The Arcadia Reptile Interactive UV Index Guide Our recommended guide for your species. ‘It is vital that we provide our pets with an accurate provision of replicated solar energy that includes the correct UV Index, the correct quantity and spectrum of visible light and quantity...www.arcadiareptile.com
And also should I use the 24 or 36 inch inch long uvb lamp for an 8x4 enclosure if it’s 12% from Arcadia?
You’ll be fine with the 24” a lot of members use that size in their large set ups, your tort will get plenty of uv from it as they bask, aim for a height of 18-20 inches from the top of the tortoises shell🙂
