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Ultimate UVB Topic - Archive

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  • Ultimate UVB Topic - Archive

    Below is one of the most popular discussions around UVB. Please feel free to add to it.

    Ok this one gets talked to death, but we still don't have a consensus. So let's discuss it here under its own heading. Here is some factual information about the light spectrum.

    Light is generally considered an electromagnetic wave.
    Wavelength is measured in Nanometers (1/1000000000 meter)
    IR is 700nm - 1500nm
    Visible light is 400nm - 700nm
    UVA is 320nm - 400nm
    UVB is 286nm - 320nm
    UVC is 200nm - 286nm
    VUV is 100nm - 200nm (vaccuum UV)

    Window glass through at least 50 websites I reviewed tonight, ranging from hobbyist, manufacturers to collegiate physics presentations on the web all agree that there isn't a significant amount of UVB light passed through. The problem with this statement is that the majority of sights just take this as common knowledge and move on. A few sites refer to the state of the energy. I will give a quick explanation

    Light hits a "transparent" object, if the energy level of the light matches it doesn't pass through. Glass lets through light that is above 350nm in general. This is to say that a lot of the light is absorbed or reflected, but what I can't find is how much is absorbed and reflected.

    At this point it requires a major study of the chemical make-up of glass and the intensity of the light and a bunch of heavy math that I am not really capable of doing at this time.

    What I have discovered through Melissa Kaplan's fine site is a couple of charts that give us a breakdown of natural sunlight and things it pass through
    A single pane window should transmit about 5% UVB, modern double pained windows will allow about half that, if they're tinted even less. If the light goes through a screen or a tank wall cut even more. So with single pane window with access to direct sunlight for part of the day you get the same output as a reptisun 5.0 bulb at 12 inches away.

    Now onto some theories....

    Barb Reader has had Timmy the Cooter for nearly 43 years. He started as a dimestore turtle. For the majority of Timmy's life he has had just window light. From Barb's story it took Timmy several years to reach adult size.

    I have had Uzumaki the Cooter for 8 months. He has had a Reptisun 5.0 bulb on for 14 hours a day, which he usually sits about 5 inches away. My turtle started at 1.75 inches and is now 4.5 inches. At his current rate of growth he will be a full grown adult this time next year.

    My theory is that the turtles grow a lot faster when subjected to longer and more regular UVB exposure. The amount of UVB given off by the light and the assumption that the window was single paned is close, just the actual amount of time the turtle is exposed differs.

    So is this form of accelerated growth good? normal?
    Anybody have a turtle before these new crops of lights came out and has gotten one since and noticed this?

    Some of the sources I used above

    Good work Michael. Thanks for the research about light and glass. However, I have a question about your theory of growth rate of your cooter. I think the first few years turts grow faster and I don't think this growth rate will continue. Also, UVB will not alter the growth rate (that is what you are proposing: your coot vs. Timmy - your turt will reach adulthood quicker). Here is why I oppose your theory.

    The first point: to reach maturity in size, it has to do with time. I mean if we feed a human the best foods and optimal condition, it's still going to take 16-20 years for a male human to grow to it's full size. If someone grew up with a lot of sun, that would say they would reach adulthood quicker? Hmmm. [

    The second point is the better nutrition (Ca and Vit D), the better the growth (i.e. bigger and stronger bones/shell). This is taken as a fact in most literature in the field (Ca + VitD = strong bones & bigger), but not necessarily maturing faster.

    I think you are mixing up point one and point two. I think your cooter will be bigger in the end and healthier with the better source of Vit-D from UVB. But it will still take 'X' number of years for your cooter to reach maturity. No matter how much UV and nutrition it gets. All this does is make it bigger and stronger, but does not make it grow faster.

    What you do think Michael?


    Isn't bigger the same as growing faster? I agree with Michael about Timmy; I figured he got his original UVB through old fashioned plate glass. It still wasn't much compared to outside. My baby RES living outside have gone from 1 inch to 2 1/2- 3 in in six months, with every other day feedings. They are also almost black from sun exposure, as they spent about six hours every day in full sun. They are NOT comparable to wild hatchlings as they don't have to hunt down their food or hide from predators.

    In humans, we have found that better nutrition leads to both taller growth and earlier puberty. I am pretty sure the sun is not a factor, but remember that we, too, need D3 for growth, and in colder climates it is often added to milk so that we get it even in the absence of sufficient sun exposure.


    Also keep in mind that there are two schools of thought about UVB and D3. It is generally accepted that most reptiles need UVB to synthesize Vit D3. There is anothe rschool of thought though that beleives the same can be accomplished through diet.
    This is getting to be an even more popular theory withthe Eastern Species of Box Turtles. Most of these animals very rarley sun themsevles and live in forests with thick canopies.

    while I personally agree that we should do the UVB anyway it just gives us something to think about!!​

    In my research, and this was more on the reptile than the physics it states that the lights we provide simulate noon time sun all day. While in nature, the levels of UV and other lights change by the position of the sun.
    Also another factor is the food that is fed to the turtle. Reptomin now is a probably a lot better than pelleted foods that were available in the 60s. I can't quite remember what Barb said about what Timmy was fed when young, but her current diets are excellent. But it seems to me that humans and other animals grow a lot faster when they are provided with more nutrients and the means to metabolize those nutrients.

    We hear a lot about people making their tortoises grow too fast. However the tortoises get pyramiding and shell deformities. But is this the result of just too much protein/fat or is it that their isn't enough calcium/d3 metabolizing going on at an equivalent rate.

    For simplicity lets say that a tort needs a ratio of 2protein - 4calcium to maintain a slow even growth. Now lets say we increase the protein intake with dogfood. Lets assume that dogfood is 12protein - 8calcium, this gets the turtle to maturity 6 times faster, but with deformities. Is it concevable that if the tort was able to metabolize the 12 protein and 24calcium that it would grow normally but 6 times faster? So to increase the amount and duration of UVB should raise the metabolization of calcium, making said turtle grow faster, without deformity.
    ***Please note - this ratio is a theoretical argument and in no way should be considered as a good ratio for tortoises, please review your species care requirements.

    I believe that any studies into this would be cruel, so I guess we'll never really know, but I think that over-abundance of UVB light helps turtles grow faster.

    This talk of animals accquiring the vitamins and minerals through diet is good. But UV light gets to the surface in even heavily forested places and it even gets through clouds. So I believe that box turtles are still getting some/enough UV to metabolize their needs. While raising your baby, I bet he will grow a lot faaster than his wild counterparts for 2 reasons, abundance of food and abundance of UV light. Even with shade in a turtle pen, it'll get more direct light than in the woods...
    Also on in one of the articles they did some tests with lizard basking spots. cold bright place vs. warm dark place and the lizards always chose the bright place, somewhat proving that the reptiles instictively knew how to regulate their UV exposure.​

  • #2
    I've ben thinking on ways to simulate a true day night cycle. Does anybody have any ideas about this. Was thinking of lights that move from one side to the other and that the intensity goes up til afternoon then starts to fade. I believe this would be even better than just a heat and strip light...

    You can buy lights that start soft and get brighter on a set ramp time. They are sold for people with seasonal affective disorder (SAD) so you might find them by searching on that topic. Moving it from side to side might be tougher.

    Since part of this discussion involves Timmy and his growth, I wanted to add what little I remember from Timmy's early years.

    Timmy was not fed 'ant eggs' which was the common form of turtle food at that time. My father got something called, "quick green flies' which was combined with lettuce, and knowing my late mother, it was probably iceberg lettuce. However, in addition, I loved to catch insects and feed them to Timmy and Jimmy, and was pretty much always digging for worms and chasing files and grasshoppers. For all I know Timmy wouldn't be here today without that.

    On the UVA/UVB front, Timmy and Jimmy shared a room with my sister (b. 1950) and me (b. 1955). They lived in what is today called a 'death pond' for their first year or six months before being moved to a 10 gallon tank. They lived there until they were about 1/2 as wide as the tank, maybe a little more. I think this was in 1965. That is when my father and I built a built-in out of lumber coated with boat epoxy. There was no sand, and if either had been female, that turtle would certainly have become egg-bound and died, but one of my books at the time said that turtle eggs didn't HAVE to be laid, and could be held in the turtle indefinately to no ill effect.

    In the early years, the turtles had no filter, but we changed their water either every other day or daily. Once in the 10 gallon tank, they had a basking platform made out of half a textured garbage can, with a door cut into it so they had a hide box. They had not basking light except the sunlight streaming in the window. The room had an Eastern exposure, and caught the morning sunlight. The tank was not kept covered, and frankly, I can't figure out how they survived.

    After they were moved to the built-in, they still had no filter, but at some time over the years I added a basking lamp and a clear pastic cover to keep the set-up humid. The cover gradually got dirtier and dirtier, and was never cleaned. However, the sunlight came in through a pane of plexiglass which was next to the window.

    Most of the windows in my parent's house had storm windows attached, as well as screens.

    I wish I could claim better husbandry for my wonderful turtle, but I can't. I read everything available to children at the time, but those books were pretty bad (I still have most of them.). When I entered high school, and took a summer science course in which I was to conduct an experiment, I sought to do it on turtle nutrition, but was told I had to use eschirica coli. (That's spelled wrong, I know; They are one-celled critters). Timmy and Jimmy might have been far better off if I had read the mid-70s scientific data on turtles, but instead I read on e. coli.

    That's the had truth. I wish I could claim better care.​

    Barb, you just have to remember. You can't look back and judge things by the standards of today. during the time period you are describing that was very good care. You couldn't have given them a UVB bulb even if you new cause they weren't available. Anyway Timmy survived and I know people that follow husbandry practices religiusly and can only dream of having their pets for so long!! [

    MichaleT, YOu may try looking onto some Reef lighting equipment. Certain things kept by saltwater hobbyists require this true day/night cycle. I've heard of equipment they use to replocate this.​

    Does anybody know how long this new crop of UVB lights have been out? Has their been any study on their actual effectiveness or long term sideeffects? From what I can tell is, no. I spent some time looking into measuring the actual amounts of UV radiation and to do this really requires a lab environment. From some study with iguanas these type of lights tend to correct and even reverse symptoms of MBD, but is their a point when they get too much? I wish I had the space to run an experiment. 1 hatchling indoors with UVB lights, and one outdoors with natural light. Then gauge growth and development rates... I wonder what we'll find out over the next ten years...

    ok, this string went all over the map but here's what i think on some of the topics

    even our best UVB sources don't come close to the suns output
    given enough to eat and good health wild turtles should out grow captives every time

    reptiles grow through out thier lives (starting fast then slowing down)
    the speed of which can be effected by the care given
    the age an animal reaches maturity can not be change

    mamals work differently than reptiles so can't be used to compare
    example: human females start thier period for the first time at 105 lbs and about 17% body fat
    age has nothing to do with it
    the high fat diet that brings on early puberty also lets to longer adultleses

    the easyest way to simulate the changes in light levels would be to have many lights on timers

    i had more but i've forgotten now and don't want read back through at this time
    got a im going on the side and i keep typing the wrong stuff on the wrong thing, maybe later​

    So if a girl never reaches 105 lbs she will never have a period. Would you care to share your sources, becuase this sounds pretty farfetched.

    Also, the comment was about the availability of nutrients and the means to metabolize them, and mammals, fish, reptiles, single celled organisms all follow the rule that more = faster and bigger

    I think the point is that the animal will get a sustained 5% UVB in an indoor setup for 12-14 hours. The suns UVB flucuates depending on hundreds of variables and time of day. I think the actual amount of absorbed UVB is in the indoor setting.

    Wild turtles almost never outgrow captive turtles. In fact I have never heard of a case of this. My comments towards Billy's hatchling is that he will get regular and knowing Billy excellent food and not have the ability to hide in the deep dark forest. Meaning that his growth rate will far exceed a wild hatchling on its own.​

    Some question was raised as to the effectiveness of UVB lights. Supposedly Boston University did a study using a combination of UVB lights and blood tests on reptiles. They noted a significant increase in the production of Previtamin D3 in the blood of the animals when exposed to UVB.

    Here is the link:

    Now I have not been able to verify this test with Boston University. I have emailed their staff a couple of times and have received no response. Others have complained about this too! So there is no verification on what ZOOMED claims!.

    Also it is not necessary to understand the physics of optical transfers. You only need to measure the outputs using a "UVB Meter". That is the final say because all else is just cheap talk and cheap theory until verified with lab equipment! Here is a link for some tests done using a "UVB Meter"...

    Michael, I believe it would be futul to attempt this. Since the intensity/power of the sun is pretty strong at high noon. There are medical grade tubes out there that can generate this amount of UVB.
    On the order of 250 Uwatts/CM.

    Very easily you can damage the eyes of the reptile (and your own) with these high power tubes. Also being medical grade tubes and very specialized I would imagine they are prohibitively expensive.​

    Ok...So what about a full spectrum florescent bulb? Would that meet the needs of a turtle? What is full spectrum? UVA,UVB,UVC,or UV? Isn't that what all those REPTI and ZOOmed reptile lights are?



    • #3
      Even if the turtle were to get D3 from other sources besides light, does it matter if you spend $30 more or less on a light- it also transmits heat.

      Not necessarily! Sometimes Full Spectrum only refers to the color of the light and not the spectrum of waves which it emits. The light in the UVB wave length is non visible.

      It reference to request above, for ways to simulate varying uva/uvb levels over the course of a day. There are dimming ballasts for available for fluorescent lights. So using something along the lines of a reptiglo 5 or reptiglo 8 or comparable bulb, and electronically dimming it in the evening and brightening it in the morning should give you simulated daylight variation.

      Since this is the most intense topic on UVB, I guess I should ask--does water have similar characteristics as glass in block UVB? I have read on the forum that it does, but it seems wavelengths are affected by chemical composition and water is definitely different from glass. Anyone got any answers?

      Hi turtlers,
      Im new here, Im from australia and keep oz species Emydura and Chelodina's. This is an intresting topic, I use a reptiglo 8.0 uva/uvb above my tank at about 6 inches from waters surface. These are really designed for desert species reptiles but are supposed to have a greater depth of penetration thru water[at full strength] so i thought id try one when my 5.0 got weak. The only real difference ive noticed is that algae grows all over the substrate and glass alot more. Im not sure that growth rate is greatly affected by uva/uvb tho. My latest babys are now 8 months old, and around 8cm diameter, in the wild both these species would take up to 4 years to reach that size. I think that has to do with having to find food and also tempature. In captivity they are kept at 25c/77f and at night at about 18c/64f year round for the first year. However research has shown corrospondance between growth rates and temp in control trials. Growth rate is significantly slower at cooler temps, lower metabolism, less food, less activity, hence the reverse would have significant effect to faster growth. Though i feed mine only every 3 days, i feed a lrg range of highly nutritious foods. In the wild however, for a hatchling food is sccarce and limited variety too, since most of its time is spent hiding from predators. Since hatchling rarely bask, at least not australian species except Emydura for most of the firstyear, i dont see how uva/uvb would be a big factor.
      Just my two cents worth anyway~cheers​

      Hey guys, Michael T asked for any stories on our experiences. I've got a couple conflicting ones:

      I got a Red Belly hatchling years ago. NO Ca supplements, no UVB. Grew normal, quick and had a hard shell. Any explanations?

      Jeff has had a different Red Belly hatchling for a year and a half. UVB (12-14 hours a day) from the start with CA supplements. Slow slow growth. She is less than 3 inches currently.

      A Mississippi Map we adopted to Kara, named Charger, measured in at 1 & 3/8" on November 20, 2002, and was 3 & 5/8" on May 30th, 2003. Inconsistent UVB.

      Jeff's Fla Chicken Turtle "The Colonel" [(from Underground Reptiles) has had UVB from the start. PERFECT, steady growth. No shell problems, healthy shedding.​