Lower UV % closer to shell

[Illusions144]

Hi all. I’m building a new tortoise table for my Horsefield tortoise and it will be in our living room. We have a hatch (old fashioned but very useful) next to where the table will be, which goes to the kitchen. We still want this to be accessible and don’t want the UV light going right across the middle of it. For this reason, I need the UV strip light to be lower down (closer to his shell) than the 12% T5 UV strip light suggests. I read that Horsefields need 3-4 UV index. Can I use the 6% T5 UV light lower down? As in this table. Thanks

 

[Littleredfootbigredheart]

Let me tag @Alex and the Redfoot he can sometimes answer to the more technical stuff

 

[Alex and the Redfoot]

Hi all. I’m building a new tortoise table for my Horsefield tortoise and it will be in our living room. We have a hatch (old fashioned but very useful) next to where the table will be, which goes to the kitchen. We still want this to be accessible and don’t want the UV light going right across the middle of it. For this reason, I need the UV strip light to be lower down (closer to his shell) than the 12% T5 UV strip light suggests. I read that Horsefields need 3-4 UV index. Can I use the 6% T5 UV light lower down? As in this table. Thanks

Hi!
Yes, you can use 6% lamp at correct distance.

However, there is one nuance: both 6% and 12% lamps have around 30% of their output in UVA spectrum band. So, technically, under 6% lamp at 10-11" there will be twice more UVA exposure than with 12% lamp placed at 18-21". For a young tortoise this can be a concern (as UVA has some aging effect on keratin).

I'll tag @jaizei and @Markw84 - interesting to know their opinion.

 

[The_Four_Toed_Edward]

How old is your tortoise?

 

[Illusions144]

How old is your tortoise?

He’s 29

 

[Markw84]

I just don't believe the 6% is a good choice for a tortoise. @Alex and the Redfoot 's comment is valid that you are concentrating UVA which is just a strong in a 6% bulb as a 12% bulb. More of consideration for me is that I feel the UV should be as "overhead coming straight down" as possible. When you use a 6% at closer range the light is then concentrated in a smaller area and spreading outward from there. A 12% at 2x the height will give a much wider UV zone with light traveling more downward over a much larger area. Also, the UVB level/strength increases geometrically with distance, not linear. So when trying to establish the proper level with a tube designed to be much closer, just a few inches will make a huge difference in intensity. With an adult tortoise, that can be quite problematic.

 

[The_Four_Toed_Edward]

I just don't believe the 6% is a good choice for a tortoise. @Alex and the Redfoot 's comment is valid that you are concentrating UVA which is just a strong in a 6% bulb as a 12% bulb. More of consideration for me is that I feel the UV should be as "overhead coming straight down" as possible. When you use a 6% at closer range the light is then concentrated in a smaller area and spreading outward from there. A 12% at 2x the height will give a much wider UV zone with light traveling more downward over a much larger area. Also, the UVB level/strength increases geometrically with distance, not linear. So when trying to establish the proper level with a tube designed to be much closer, just a few inches will make a huge difference in intensity. With an adult tortoise, that can be quite problematic.

Could a T8 work in this case?

 

[Alex and the Redfoot]

Could a T8 work in this case?

This won't resolve issues, Mark outlined above. UVA output of T8 lamps is much lower, though. But T8 lamps have shorter lifespan in closed chambers than T5 lamps.

If available height is a bit less than recommended (e.g. 16-18") it's possible to use lamp guard mesh cover with a Desert lamp. At the distance of 18" ZooMed Reptisun 10.0 can be used (they have slightly lower output, probably because of reflector shape).

 

[jaizei]

I more or less agree with what Mark said, I strongly prefer UVB and other bright lights to be mounted as high as possible so that they're in the animals line of sight as little as possible.