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Temp/UVB Help

PostPosted: Wed Aug 14, 2019 10:14 pm
by Gerstein
So I am currently re configuring the Heat/UVB Lamp combo (Using a dual fixture by Zoomed). I could use some advice regarding both temperature and UVB

Turtle: Shelldon Leo Kooper, Red Eared Slider, been with me 10 years
Previous Set Up:
Lamp: Zoo Med Dual Fixture
Heat Bulb: 50 Watt Reptibasking Spot Bulb (Zoomed) 12 Inches Away;
UVB Bulb: Exoterra UVB 100 12 Inches Away
Basking Area: Slate Tile 'Throne' with eggcrate ramp.
Zilla Fresh Air Screen covering Tank

(Basking Area, Lamp Fixture, and Fresh Air Screen will remain the same)

My current goal is to set up some lamps that are a tiny bit closer to the throne, which will help for future tank upgrades I am currently planning (Having the lamps hanging too high will create problems for a higher tank)

Temp Question: Experimenting with a 25 W Zoo Med, and for the most part it is better. I am having difficulties obtaining consistent temperature measurements. I am using two zoo med thermometers; one a standard dangly one (Dangler for Short), and one an infared thermometer (Calling it Red for short). I am trying to get measurements from the 25 bulb to the basking about 7 inches away. Measuring beneath the hottest part of the lamp, Red measures it at about 88-90 which is beautiful and exactly my goal (if the ideal temperature range is about 85-95, then 88-90 is that neat middle, and 88 is around 10 degrees higher than the water temperature). Dangly says it is about 95.2 (after some time has passed) which is less neat. I don't understand why the two thermometers are saying such different things... They seem to agree on the water temperature. Red gave measurements that gradually increased the closer I got to the light and Dangly was somewhat similar but they are apart by 6 degrees... I was wondering if anyone had any input for which thermometer is more accurate? I just got Red today and until now I was using Dangly.

UVB Question: So I am hugely stumped on how much UVB my turtle should be getting. Exoterra has done its job well, for sure (changing bulbs every 6 months and her last physical two months ago went very well), but when it comes to measuring UVB and how much Shelldon should be getting, I am stumped. In experimenting with Temperature and UVB combinations, I ordered some Zoomed UVB Bulbs (10.0 Mini Compact), which I will be testing when they arrive. Either way though, I have no idea what to do with the numbers that I get when I measure the UVB (USing a Zoomed UVB Meter, measuring it in µm/cm2). Zoomed has a neat little chart, but it lists recommendations using the UV Index. I do not know how to convert UVB Measurements in µm/cm2 to the UVI (not for lack of trying). Furthermore, recommendations vary wildly from source to source for a red-eared slider. According to the box of the bulb, the RES should get 8-20 µm/cm2 (According to the annoyingly unspecific star system they use, and the back of the bulb package). A friend of mine said that 140 would be good (albeit conservative implying that slightly more would be even better) leaving me quite lost as to how much an RES should get (Whether it is a minimum or a range). I am following the bulbs directions (whether it is zoomed at around 7 inches, creating a furgerson zone of about 3-4, or exotera about 12-16 inches) but I want to know that Shelldon is getting the right amount of UVB using exact units rather than annoying 'rating systems'.

My initial plan was to use the 25 W Zoo Med Reptibask Heat Bulb at about 7 inches away from the throne, and the Zoomed 10.0 UVB Mini Compact around 7 Inches away (According to the instructions by zoomed and fergurson zones ... 018-07.pdf . Long story short, I want to get measurements in units and I have the means to do so (Two Thermometers and UV Meter) but am having difficulties measuring/interpreting measurements. Any help would be appreciated.

Re: Temp/UVB Help

PostPosted: Fri Aug 16, 2019 7:48 am
by ljapa
For more than you want to know about reptiles and UVB, check out the linked PDF at

They looked at reptiles in the wild and measured time of day, basking substrate temp and UVI using a Solarmeter 6.5, which measures UVI. That’s where your guides on the lights came from. They use the idea of Ferguson Zones, which divides UVB into four categories. Their quick chart lists RES as zone 3, but on page 20, their detailed chart lists RES as zones 3-4 and the basking temp at 35 Celsius, or 95 Fahrenheit.

They define the zones by UVI, but they give descriptions of 3 and 4 as “open or partial sun basker” and “mid-day sun basker.” I live near Chicago at the extreme Northern edge of the RES natural range. I see them in the wild on dog walks and can confirm they are basking in noon sun around solstice time when I’d never think about venturing out without sunscreen.

The people behind that research have information about using Solarmeter UVB detectors at

They were the first group to start using the 6.2 and likely are the reason you and I have heard of it. They’ve moved on to the 6.5 because it’s sensitivity range better matches the D3 portions of UVB. They have this to say about the two meters at that link:

Its broadband response (typical of all UVB meters) to the entire UVB waveband, however, causes a problem if we want to compare the ability of different lamp brands to enable vitamin D3 synthesis, or to match up sunlight and lamp UV levels. Solar Vitamin D3 synthesis almost all occurs between 290 - 315nm, but the shorter the wavelength, even within this small range, the greater the effect.
In theory, if one lamp had most of its UVB in the shorter wavelengths, e.g., below 305nm, whereas another had most of its UVB in the longer wavelengths, e.g., above 315nm, they could both give identical readings with a Solarmeter 6.2, but the first lamp would be much better at producing vitamin D3 than the second one.... it might even have unwanted UVB from below 290nm or even UVC, and cause skin or eye damage.......

I was looking into this a few weeks ago and found a great site discussing this with bandwidth charts comparing the two meters, but I can’t find it now.

I bought a 6.2 years ago, but the dog chewed on the leather case and broke the meter. I just this week got a 6.5 to replace it.

I’m using a MegaRay UVB bulb. I seem to remember aiming for around 100 on the 6.2, plus or minus 5, when I was targeting the basking platform for my RES with the 6.2 and after active research back when everyone was using the 6.2.

EDIT: with a dual lamp setup and a large enough basking platform, you’re probably ok having sections that a bit high and providing room for your turtle to move around and find the sweet spot.

Re: Temp/UVB Help

PostPosted: Fri Aug 16, 2019 2:20 pm
by Gerstein
Thank you so much! This information was very helpful!

Shelldon has a lot of room to maneuver around her 'throne' (it is around twice her size) so she can definitely find the sweet spot. I had just installed the reptisun last night and she was basking under it this morning.

I clocked the UVB at around a range of 40-200 µm/cm2. The meter was moved from the left to the right, with the lamp shining in the middle. In the middle, directly below the light, it seemed to settle around 140-170, which fits with my friend's recommendation, and there are spots where it is around 100, fitting in with your previous target. It seems to be an appropriate range. The maximum of around 200 was when the meter was raised slightly (And the meter itself is taller than Shelldon).

Temperature measurements were as follows:

Flat Measurement: Range of 78-89 °F (Left to Right- Around 88-89 directly underneath the lamp)
Figure Measurement (Using Red Eared Slider Figure) 87.0

Flat Measurement: 89.2°F (31.22222°C) (304.3722 K) (Beneath Lamp-Flat)
Figure Measurement: 92.0

It seems to be in an appropriate range.

Thank you for your help.

Re: Temp/UVB Help

PostPosted: Fri Aug 16, 2019 6:07 pm
by litefoot
For beginners I tell them to get separate fixtures . Heat bulbs and UVB bulbs need different placements especially if not balanced between the two. Make's it easier for beginners.
Being you have 10 years you understand about placement.
I use Mega Rays with supplemental heat when needed in a double fixture. Only difference I have a inline dimmer on my heat bulb. This allows me to adjust one degree at a time to balance them for what Piggley likes much better like in the winter. Just make sure if you do that too it's a dimmer rated for the wattage you use with the heat bulb.
You larger basking area is great so Shelldon can pick what she wants and when. Piggley's basking area is 4x's his size and also has another dock as a dry dock so if he wants to just dry off without heat he can do so .
Doing good , how about some pictures.