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As ive read floresent UV light will need to be replaced every half year or so.. Does anyone know of a way you measure the UV output without expensive testers??

A UVB meter is really the only way to measure UVB output (I've been looking at them and they're expensive, a long way off for me). If you want to see what the UVB output of some different brands are, though, take a look at http://russiantortoise.org/uvb.htm

marisa wrote: If you want to see what the UVB output of some different brands are, though, take a look at http://russiantortoise.org/uvb.htm

So if I look at his correctly;

Regular sunlight is is like 100 - 200 UVB (microwatts/cm²)

And the reptisun 5.0 is 10 UVB (microwatts/cm²)

1 hour of direct sunlight is about the same 10 - 20 hours of the standard UVD bulb?

Doesn't that make the UVB bulb almost worthless? Say the turt spends 5 hours a day basking, thats the same as taking him out in the sun for 10-15 min. Granted some places have more sun than others but the gap is still huge.

Can anyone verify these numbers?

You're correct in that a UVB bulb can't compare with the UVB output from the sun. If your turtle is out in the sun for a few hours at a time about 3X a week on a regular basis, you could do without the UVB light. The problem is being able to provide that consistently year-round. The UVB light is added insurance that your turt will be getting at least some UVB rays on a consistent basis.

Some info on the sun's UV rays which shows how strong they are:

--Clouds weaken sunlight, but thin clouds allow as much as 80% through.

--Even 1.5' underwater, UV rays are 80% as strong as in direct sun. At 3' under the surface, they're 70% as strong.

--O2 and nitrogen molecules, other particles andnclouds scatter or reflect UV rays.

--About 40% as much UV light reaches shaded areas as sunlit areas.

(The above was in USA Today on 6/27/05. Sources are the Nat. Weather Service, EPA and the Weather Channel.)

i think for a UVB light you should replace it about once a year, not once a half year. thats wat the pacage if my UVB light says. so i wouldnt worry about it until a year has passed. then just go buy another one.

Marisa,

Thank you for the for the insight. I'm not about to get rid of the UV bulb, but I'm going to be doing some better research befroe I buy another one.

I was just surprised at how little they put out.

Flourescent bulbs like Reptisun have been proven to be reliable and seem to have been the norm (and probably still are) until lights with higher UVB outputs and the combo mercury vapor bulbs came along. You'll get disagreement as to which of the latter is best (which I think ultimately means most reliable/lasts the longest).

UVB lights emitting 2% UVB are inadequate for turtles.

I have used 3% UVB flourescents and because the UVB output is so low to begin with, I've replaced them in 6 months. (And because of their relatively weak UVB output they need be closer for the turt to benefit.)

Bulbs with higher UVB outputs and the mercury vapor bulbs have instructions on the package/in product descriptions for when to replace (and distance they should be from the turtle).

Unfortunately, the only way to know if the bulb is emitting what it should or to know when it's really time to replace it, is to test it with a UVB meter. And they're not cheap. The one I want is $179.00, and that's a long way away for me.

They do get some Vit D3 from foods that contain it (good turtle pellets contain some), but there's some debate as to how efficient absorption is in this manner. A combination of some in the diet and a good UVB light is probably the safest way to go.