About UV lamp placement

mogus_a · 2026-06-04T10:09:27-0700

Hi,

I have a little ~9 month old russian tortoise.
Of course I've had a UVB lamp and heat lamp setup from the start. Temperature is easy to measure, but I've been worried about the UVB, since you can't really know if it's too little or too much or what (and I can't justify dropping 400€ on a Solarmeter).

Well now I found someone who rents out their Solarmeter 6.5R, so that's perfect. I'm now doing some measurements with it and are running into some problems.
Directly under my Arcadia LumenIZE Pro T5 (with D3+ 12% UVB 55cm (24W) lamps with brightness set to 100%) the meter reads like up to ~15 (which is obviously way too high), but on the prime basking spot the meter barely reads 2. Ok, sure, I could shift the lamp over to be directly over the prime basking spot and dim the T5 way down, but obviously I can't have the LumenIZE be under my heat lamp, it would block the heat and probably overheat/destroy the LumenIZE. So what is supposed to be done here?

The attached picture here is of the enclosure basking side to illustrate better what I mean.
This makes me think of at least one thing that could make this better: rising the LumenIZE to be higher up, like way higher up. But that is not easy to do. I guess I could 3D print very tall feet that hold the LumenIZE higher. Or maybe 3D print feet that hold the LumeIZE tilted so that it would point more towards the basking spot. Or something else? I'd love to hear suggestions on what to do, thanks.

The_Four_Toed_Edward · 2026-06-04T12:11:21-0700

Maybe @Alex and the Redfoot can help you? I remember him having experience with the LumenIZE fixture.

Tom · 2026-06-04T17:16:05-0700

As long as the basking lamp is near the UV tube, it should all work. The minimum distance recommended for the 12% HO tubes is 45cm above the top of the tortoises' shell. I often have to have them closer to 50cm.

Alex and the Redfoot · 2026-06-04T20:51:11-0700

Hello!

Generally, distance from the lamps should be right opposite to what I see on the photo:
1. Basking lamp is usually 10-12" (25-30cm) above substrate (to reach ~95F, 35-36C over basking area)
2. As Tom said, Arcadia ProT5 12% kit is at 18-20" (45-50cm) above substrate (aim for UVI 3.5-4)

LumenIZE fluorescent lamps should not be used in dimmed mode all the time - at low brightness they can flicker and dimming shortens lamp lifespan.

You can use lamp stands, similar to what you have for the basking lamp dome, to hang the UVB fixture or make a simple wooden frame. At the time of being - shut off UVB completely. UVI 15 is plainly dangerous.

Another thing to be aware of is "shadowing": when lamp fixtures block light coming from another (e.g. basking lamp dome blocks UV coming from T5 tube). Here you can find more details: https://tomaskas.co.uk/what-is-uv-shadow-and-how-do-i-avoid-it/

mogus_a · 2026-06-05T01:04:31-0700

Alex and the Redfoot said:
Hello!

Generally, distance from the lamps should be right opposite to what I see on the photo:
1. Basking lamp is usually 10-12" (25-30cm) above substrate (to reach ~95F, 35-36C over basking area)
2. As Tom said, Arcadia ProT5 12% kit is at 18-20" (45-50cm) above substrate (aim for UVI 3.5-4)

LumenIZE fluorescent lamps should not be used in dimmed mode all the time - at low brightness they can flicker and dimming shortens lamp lifespan.

You can use lamp stands, similar to what you have for the basking lamp dome, to hang the UVB fixture or make a simple wooden frame. At the time of being - shut off UVB completely. UVI 15 is plainly dangerous.

Another thing to be aware of is "shadowing": when lamp fixtures block light coming from another (e.g. basking lamp dome blocks UV coming from T5 tube). Here you can find more details: https://tomaskas.co.uk/what-is-uv-shadow-and-how-do-i-avoid-it/

I have the heat lamp 57cm above basking spot, and it is dimmed down a lot as well to make the temperature ~35C. I'm using Arcadia 75W Halogen Heat Lamps.

I guess I could buy way lower wattage heat lamps and move it closer, but I don't really see the reason (price difference is minimal as well), nice to have to heat lamp out of the way and high up, unless?

And yes, the 15 UVI is not actually being reached, I just said it as an example when using at 100% brightness. Also I was definitely not measuring at shell height, I was just saying the numbers as an illustration that it seems very difficult to get a good UVI number on the basking spot, because seemingly the number will always be MUCH higher directly under the UV lamp as opposed to the side, but I can't of course have the heat lamp and UV lamp on the same spot because one will shadow the other. But I guess I should tilt one or the other and also raise the UV lamp to be much higher. Raising it higher will surely help with the problem of having much higher UVI directly under vs to the side. I'm just not really sure how I should raise it higher though, as you mentioned I can probably look to buy some sort of lamp stand for the LumenIZE.

Also, interesting that you say dimming the UV reduces the lifespan. I thought LumenIZE and the Arcadia T5 tubes were marketed as dimmable combo? But despite that I should always run 100% and just make sure I raise it high enough? I have also used the schedules on LumenIZE to fade the UVB brightness in and out at the start and end of day. Thoughts on that then?

mogus_a · 2026-06-05T01:07:40-0700

mogus_a said:
I can probably look to buy some sort of lamp stand for the LumenIZE

I would love to see a product link to a stand like this. Or an image so I can try to reverse image search for one.

mogus_a · 2026-06-05T01:24:20-0700

mogus_a said:
I would love to see a product link to a stand like this. Or an image so I can try to reverse image search for one.

I guess one of these would be ideal, if someone just sold one wide enough for the LumenIZE.
Just hang it off that with two chains. I can't seem to one that's wide enough though.

jaizei · 2026-06-05T01:41:51-0700

mogus_a said:
I guess one of these would be ideal, if someone just sold one wide enough for the LumenIZE.
Just hang it off that with two chains. I can't seem to one that's wide enough though.

View attachment 400830

Just take the part with the hook off and slide a piece of metal pipe/tubing/conduit over the arm. If it needs more support, use 2 of the stands with the pipe in between.

The_Four_Toed_Edward · 2026-06-05T03:17:11-0700

mogus_a said:
I have the heat lamp 57cm above basking spot, and it is dimmed down a lot as well to make the temperature ~35C. I'm using Arcadia 75W Halogen Heat Lamps.

I guess I could buy way lower wattage heat lamps and move it closer, but I don't really see the reason (price difference is minimal as well), nice to have to heat lamp out of the way and high up, unless?

And yes, the 15 UVI is not actually being reached, I just said it as an example when using at 100% brightness. Also I was definitely not measuring at shell height, I was just saying the numbers as an illustration that it seems very difficult to get a good UVI number on the basking spot, because seemingly the number will always be MUCH higher directly under the UV lamp as opposed to the side, but I can't of course have the heat lamp and UV lamp on the same spot because one will shadow the other. But I guess I should tilt one or the other and also raise the UV lamp to be much higher. Raising it higher will surely help with the problem of having much higher UVI directly under vs to the side. I'm just not really sure how I should raise it higher though, as you mentioned I can probably look to buy some sort of lamp stand for the LumenIZE.

Also, interesting that you say dimming the UV reduces the lifespan. I thought LumenIZE and the Arcadia T5 tubes were marketed as dimmable combo? But despite that I should always run 100% and just make sure I raise it high enough? I have also used the schedules on LumenIZE to fade the UVB brightness in and out at the start and end of day. Thoughts on that then?

Halogens are not recommended for tortoises as they create a spot that is too concentrated and can have a dessicating effect on the shell.

mogus_a · 2026-06-05T03:40:22-0700

The_Four_Toed_Edward said:
Halogens are not recommended for tortoises as they create a spot that is too concentrated and can have a dessicating effect on the shell.

Omg. Seems I can't do anything right. Is this for sure really a problem when I have it almost 60cm up from the substrate level and I measure with temperature sensors that the temp is ok?

At first I had non-halogen lamps, but I had huge problems with multiple of them burning out within a few days. Maybe it was caused by bad contact with the fixture or whatever, but I got these halogen lamps and now it's been working flawlessly. I was so happy to have something that works. And now I even have extra 2 lamps in storage. But now if these are no good then I've wasted a lot of money and have to try to find a fitting bulb once again.. So frustrating.

(I have an Arcadia Ceramic Reflector Clamp Lamp 14cm fixture)

The_Four_Toed_Edward · 2026-06-05T10:59:03-0700

mogus_a said:
Omg. Seems I can't do anything right. Is this for sure really a problem when I have it almost 60cm up from the substrate level and I measure with temperature sensors that the temp is ok?

At first I had non-halogen lamps, but I had huge problems with multiple of them burning out within a few days. Maybe it was caused by bad contact with the fixture or whatever, but I got these halogen lamps and now it's been working flawlessly. I was so happy to have something that works. And now I even have extra 2 lamps in storage. But now if these are no good then I've wasted a lot of money and have to try to find a fitting bulb once again.. So frustrating.

(I have an Arcadia Ceramic Reflector Clamp Lamp 14cm fixture)

Maybe @Alex and the Redfoot can explain better what the problem with halogen is.

You don't hang the fixture using the clamp do you? They are prone to failing and thus a fire hazard. Is the 14 cm the diameter of the dome?

mogus_a · 2026-06-05T12:08:02-0700

The_Four_Toed_Edward said:
You don't hang the fixture using the clamp do you?

Nope, I actually have the stand I sent a picture of a few messages ago. And yeah, the clamp seemed useless/bad when I saw it in the box/tested it.

The_Four_Toed_Edward said:
Is the 14 cm the diameter of the dome?

I'm not home right now to check, but I guess so. It's the one that's sold with 14cm in its name.

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