UVB Bulb rating


New Member
I have been in the process of testing and replacing my UV bulbs and found that I'm buying ones that don't seem much better then the ones I'm replacing.

So, those of you who have meters, what is your scale? I measure 8" from the bulb and replace at 18 to 20 depending on the size of the cage. New bulbs usually measure in at 38 to 40, however I am finding way too many coming in at 20 to 24. That sure doesn't give me much life for the cost of the bulbs.

Does anyone else test their bulbs?
When you take the measurement at 8" is that through the screen at the top of the cage or is it unobstructed? Are you using a reflector of any kind?

I just measured my 5 month old Reptisun 5.0 and had a measurement of 34 microwatts at 8'' through the screen. I use an Arcadia reflector that is pretty highly polished

I would either replace at 20mw or us two bulbs 20mw and check the readings again.
I measure the used bulb while in place in the fixture over the cage. I measure the new bulb when I put it in the fixture on the table. I always keep a log. I have numbered all the fixtures and put a label on the fixture with the date I placed the bulb and the reading at that time. The same information goes into the log since I can't always read the tag on the fixture later on.
I really hope to get a meter with my tax return cash! I hate changing bulbs not really knowing if I've waited too long or if they're still good. I always date the fixture and try to replace bulbs at around 6 or 7 months. What kind of lifespan are you finding with your readings? Cheers!
Having a meter also helps me with placement of limbs and perches. I try to position the upper branches and vines where they get around 35 micro watts of UVB.
Assistance please. No where else to get info.

I guess I am unclear as to an answer so I am going to restate. I am going to check all my bulbs today, not through the screen but on the kitchen table at a distance of 8" away from the bulb as my basking perches are all 8-10" from the top of the cage.

1. What should a new bulb read with my solarmeter 6.2 (highly recommended to me as the best for my purposes)?

2. At what reading should the bulb be changed?

3. Should I make any changes in the distance I measure the UVB's?
I don't have a new tube to measure, but I just checked my current tube for you. From 8", with a reflector and not going through a screen, I am getting a reading of 61 microwatts at the center of the tube using a Solarmeter 6.2. Keep in mind all reflectors are not created equal. Meters will not always read exactly the same.Temperature and humidity can also affect the readings

I will change my tubes when the UVB measured at the basking spot through the screen top approaches 20 microwatts.

The distance you measure the UVB from is arbitrary if you are only using it for comparison purposes among your own tubes.

Your data might be easier to interpret if you standardize your methodology. I take all my readings through the screen top of the cage from a spot 2" above the highest basking spot my cham uses. That is the UVB my cham is receiving and consequently the only reading I find important.
I have a lot of cages, but I'm reorganizing my rooms while I measure my bulbs, so I'll meter them inside the cage. I can use foil as a reflector. That might give me a higher reading.
I have a lot of cages, but I'm reorganizing my rooms while I measure my bulbs, so I'll meter them inside the cage. I can use foil as a reflector. That might give me a higher reading.

If you aren't using any reflectors the foil will definitely increase your UVB output.
what about a T5 fixture.. are those to low of a light output? or should it be fine with a nice zoomed cfl 26 watt 5.0 uvb raiting also? the lil 20 inch T5 is also uvb 5.0 i belive. Rzilla makes the tube.
Aluminium flexible sheet is the best solution for maximizing light availability withing the room. The sheet reflects more than 95% of the light and directs it back to the directed area, thus maximizing the light available to the encloser which in turn maximizes lighting to the maximum... just something i use in my green houses. and read up on. Aluminium really just soaks light up, read up on it. just light reflectors. anyways yeah im new to this forum but like to be nosey lol o and not aluminium foil it does not reflect. it more or less just just soaks it up.
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