# Changed UV light to Reptisun T8 10.0, 13” distance ok?



## MoreCowbellAz (Oct 12, 2019)

Still tweaking my baby DT enclosure, I just converted from a MVB to the above mentioned 24” tube type UVB, and to start I set it at 13” from the substrate, so figure 12” from light to shell. Does that seem about right? I see some conflicting info, their quick lighting facts sheet says 10”-18”, while their color coded chart on the web site suggests something a little closer like 8”-12” for mostly full sun animals. I don’t want to overdo it, esp since he’s so small, but I also Don’t want to defeat the whole purpose of getting him some extra UVB. 

He’s got a basking bulb on the warm end of the enclosure, so heat is covered.


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## MoreCowbellAz (Oct 12, 2019)

Also, I was planning on ordering a UV meter and it occurred to me, even if I had one I don’t know what reading I should be going for. I see a lot of recommendations to get a UV and avoid the guess work, which I like, but I’ve not seem much about what numbers are good, especially for. DT. The Zoomed site says 1 to 2.6, but that seems low from the little bit I’ve been able to find. 

Can anyone tell me what UVI numbers I should be going for? I assume once I have a good target then I can dial the height in.


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## Markw84 (Oct 13, 2019)

MoreCowbellAz said:


> Still tweaking my baby DT enclosure, I just converted from a MVB to the above mentioned 24” tube type UVB, and to start I set it at 13” from the substrate, so figure 12” from light to shell. Does that seem about right? I see some conflicting info, their quick lighting facts sheet says 10”-18”, while their color coded chart on the web site suggests something a little closer like 8”-12” for mostly full sun animals. I don’t want to overdo it, esp since he’s so small, but I also Don’t want to defeat the whole purpose of getting him some extra UVB.
> 
> He’s got a basking bulb on the warm end of the enclosure, so heat is covered.


I know most people seem to hate the answer and balk at cost, but a UV meter - solarmeter 6.5 = is really the only way to tell. Even individual bulbs can vary depending upon the type and quality of fixture they are put in, so just saying a T8 10.0 is often not enough!.

If you keep the UVB light on all day, I would say a reading of 2 is good. I use a reading of 3.5 - 4.0 for my tortoises, but only have the UVB light on for about 6 hours midday. Watch your tortoise for basking habits. An incadescent bulb providing heat should be right next to the peak UVB zone as heat encourages basking along with brighter light. Some tortoises tend to be morning baskers, using the sun to heat up and start their metabolism and avoid the heat and high UV levels of midday. Desert Tortoises often follow this pattern. IF so, perhaps a UVI of 4.0 and on from 8AM to 1 PM would be a good goal.


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## Tom (Oct 13, 2019)

In my experience with that particular bulb, it needs to be no more than 9-10 inches away to get a reading of 1-2 on the UVI from a Solarmeter 6.5. They don't make a lot of UV, so they are pretty safe and you don't have to worry about overdoing it. I also found that after 3 years of continuous use for 12-13 hours a day, both of my bulbs were still making the same UV levels as when they were new. Glad I didn't replace them every six months like some people do.

As Mark said every bulb coming out of the factory can vary, and different batches do vary. The fixture also makes them vary, so a meter is essential to know what is going on over your tortoise. When you get your meter, take measurements and come back and share so we can all learn.

I like a reading of 5-7 and only run my bulbs for 3-4 hours mid day. I use the Arcadia 12% HO type. A wide variety of strategies can work, and different people have different views on this matter.


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## Sterant (Oct 13, 2019)

Also keep in mind that the reflector in your fixture matters. A high quality polished aluminum reflector can nearly double the downward UVB as compared to no reflector or a junk one. I run T5 HO bulbs (reptisun 10.0). I try for a reading of 5 - 7 for adults and can get it with the fixture about 18" above the substrate. These bulbs can also last 3 years.


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## MoreCowbellAz (Oct 14, 2019)

Thanks for the responses. I ordered a Solarmeter 6.5, in the meantime I'll leave the UV light at 12" over shell, he does get 3-4 hrs of some outdoor sunlight and that'll give time time actually measure the UV when the meter gets here. The hood is a Zoomed Reptisun T8, 24' bulb, so we'll see what it puts out. I'd prefer to not have to make it super low, I don't want it so low it blocks my view. So we'll see, if nothing else I'll upgrade to an HO hood and bulb and re calibrate, should be easy with the meter.

FYI, right now I have the UV on the same timer with the basking light, 6:15am - 6:45 pm, I did both together (one on each end) so it's bright and I'm not letting him hibernate. So since it's on all day I don't need intense UV, I just like knowing he's covered in case I'm not able to get him outside as long as I'd like.


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## MoreCowbellAz (Oct 24, 2019)

Ok I received my Solarmeter, took a few quick readings, only had a min so I'll be more through this weekend. With the above ZooMed bulb and housing/reflector, it seems to be pretty inline with what Tom was describing above. I also noticed UVI is about half towards the ends of the bulbs as what I see towards the middle. I din't know that.

Right end, distance 8.25", UVI 1.4
Midway, distance 8.75", UVI 3.2
Left side, distance 8.75" UVI 1.9

Def no danger of scorching the little guy.

I also took a reading outside at around 12:30, full sun, reading around 3.4. In complete shade but outdoors around 1.0. Indoors complete shade 0. The outdoor share reading was interesting to me, must be from reflecting rays bouncing around?


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## MoreCowbellAz (Oct 24, 2019)

I forgot to mention that I haven't decide upon my next steps, if I should leave it alone and let it have that gradient from area to area, or raise it so the center peak spot is more like 2 or so since it's on 12.5 hours a day, or maybe even lower just one side to even the gradient out. Not sure there. The UV is on one end, the other end has the basking bulb, and he seems to move around the enclosure pretty evenly although I dont see him sleeping on the cool side very often, he has a favorite hide on the other side (but not directly under the basking bulb).


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## Tom (Oct 24, 2019)

MoreCowbellAz said:


> I forgot to mention that I haven't decide upon my next steps, if I should leave it alone and let it have that gradient from area to area, or raise it so the center peak spot is more like 2 or so since it's on 12.5 hours a day, or maybe even lower just one side to even the gradient out. Not sure there. The UV is on one end, the other end has the basking bulb, and he seems to move around the enclosure pretty evenly although I dont see him sleeping on the cool side very often, he has a favorite hide on the other side (but not directly under the basking bulb).


I think it is fine as is.


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## MoreCowbellAz (Oct 25, 2019)

Thanks, I was trying not to over-think it so that's where I'll start. So what I'm ending up with is he's got low level/long duration UV in his enclosure that supplements the natural sun he gets around 3 hours a week (he's outside more than that but I'm talking time he's actually in direct sun. Yes, I actually time him lol). That makes some logical sense to me that would be a decent balance that's effective. 

Having the meter is very interesting I'm finding. As I said before I didn't realize with those UV tubes the level changes along the length of the tube. This morning I was outside at 8am, full direct sun, zero clouds, it was actually a bit hot standing in the sun, and the UV reading was barely above 0!!!!! I think those meters are worth the money, I tend to be the type that hates guess work, I want actual data on everything. Lol.


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## MoreCowbellAz (Oct 25, 2019)

BTW, I'm surprised this ZooMed T8 10.0 bulb isn't more powerful, the way they market it. Do you think they're just building in a safety factor for uninformed/irresponsible users who might put it way too low and not paying attention? Seems crazy to me that to have effective UV it needs to be at 9-10", they say it's good up to 18". I haven't measured it at 18" but I have to guess it's zero. I'm not sure what good the 5.0 would be.


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## Dovey (Oct 25, 2019)

MoreCowbellAz said:


> Still tweaking my baby DT enclosure, I just converted from a MVB to the above mentioned 24” tube type UVB, and to start I set it at 13” from the substrate, so figure 12” from light to shell. Does that seem about right? I see some conflicting info, their quick lighting facts sheet says 10”-18”, while their color coded chart on the web site suggests something a little closer like 8”-12” for mostly full sun animals. I don’t want to overdo it, esp since he’s so small, but I also Don’t want to defeat the whole purpose of getting him some extra UVB.
> 
> He’s got a basking bulb on the warm end of the enclosure, so heat is covered.


We seem to be going through the same process for the same species at the same time...Paisano! Thanks for the UVA reminder.


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## Markw84 (Oct 26, 2019)

MoreCowbellAz said:


> BTW, I'm surprised this ZooMed T8 10.0 bulb isn't more powerful, the way they market it. Do you think they're just building in a safety factor for uninformed/irresponsible users who might put it way too low and not paying attention? Seems crazy to me that to have effective UV it needs to be at 9-10", they say it's good up to 18". I haven't measured it at 18" but I have to guess it's zero. I'm not sure what good the 5.0 would be.


Most reptile enclosure on the market, or converted aquariums, just don't have the height to be able to use a T5. SO there are useful applications for the T8s when enclosure height is limited to 18" or less total. It is a function of your height requirements as opposed to manufacturing the highest output bulbs all the time.


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