Lighting thoughts and experience over the past decade

turtlesteve

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So, I've bought and used a whole bunch of tortoise lighting over the past decade. I have considered writing down some notes before, but really felt like it would be pointless if I didn't have UV data. So I finally broke down and bought a Solarmeter 6.5R, and got UV index measurements on what I am still using. I have no idea why I didn't get one before - it took me about 5 minutes to confirm how critical it was. So, in no particular order, here goes:


MERCURY VAPOR BULBS: (Powersun, Exo-Terra Solar Glo, Mega Ray). This was the first lighting method I ever used. I've used both 70W, 100W, and 160W bulbs and all 3 brands. I have probably burned through 15 bulbs in a decade, give or take. Honestly, never having a UV meter, I would use them until they burned out. The life of the bulbs is highly variable and I probably get 12-14 months on average (when they burn out). As far as UVI measurements: On a brand new 160 watt powersun, I get a UV index of 3.4 at 24" (I will not mount them any closer than this, because they get too hot). So, pretty good. BUT I also tested two bulbs that were a year old - a 160 watt Solar Glo and a 70 watt Mega Ray. Both of these read almost zero (0.1-0.2) UV index at 24", and neither of them exceeded 3 even with the solarmeter almost touching the bulb. So, a year later, these two bulbs are functionally useless.

Pros: Honestly I can't think of much. I am so done with MV bulbs. I am still using them, only because I haven't run out of spares.
Cons: Well, obviously, the UV output is not stable. I have no idea if one brand drops off more quickly than the others, but I will monitor the new bulb over time and give updates. They produce tons of heat and the fixtures get hot enough to cause burns.

FLUORESCENT T8: I have used the Zilla Slimline desert fixture (the 18" model with a 15 watt bulb). I have only started using these fairly recently, and have two of them running right now. One of them is 6 months old and the other is about 14 months old. For UV measurements, both fixtures give me exactly the same readings - UV index is about 3.0 at 8", and it's about 1.0 at 16". I have no idea how long the bulbs last, I haven't burned one out yet. I also discovered that if the clear cover over the bulb is removed, the UV output increases by about 40-50%. So I immediately removed the cover from one fixture on a hatchling enclosure, which was mounted at 16", and got the UVI up to 1.5.

Pros: The fixtures are reasonably well made. It appears (so far) that the UV output is stable for at least a year. I can use them inside a closed chamber with minimal heating. I like the compact size of the fixture.
Cons: Low UV output, making the proper mounting height too low. I have one mounted at 10" and one at 16", and I much prefer mounting them higher to get wider coverage.

FLUORESCENT T5: I used the Arcadia 12% bulb (bought with a fixture online). I bought it with some cheap fixture that seems to be the standard offering everywhere I look. I don't have UV measurements, because either the bulb or fixture died on me and I haven't gotten a replacement yet. It lasted about 2 years.

Pros: To be determined based on UV readings when I get a new one. Hoping better UV than the T8's.
Cons: The fixture I got with it is crap, but this is nothing on Arcadia as they didn't make it.

HID (HIGH INTENSITY DISCHARGE) lighting: I am using the Solar Raptor 70W flood. I believe this is a metal halide bulb. This is a light that's marketed in Europe and hasn't really made much inroads in the US, but seems like other brands are offering HID now. They had a sales rep at the Pomona, CA show one year when I was there, and I bought one. Remembered thinking I was crazy, because of how expensive it was to set up (the bulb cost is not so bad, but you need an external ballast and fixture to get started). I have been using this light for about 7 years (!) with the original bulb. I measured it today, and I'm reading UV index of 2.4 at about 12" (where I have it mounted). The other interesting thing about the solar raptor bulb, is that the glass face plate of the bulb is actually not sealed, it snaps into the reflector and the actual bulb behind it is very small. Well, at one point, the face plate fell off and was captured by the screen on the light fixture. So out of curiosity, I did a UV reading this way and got a UVI value of 10-12 in a very narrow beam. I'm going to do some more testing, but it's clear that the face plate is either greatly attenuating or dispersing the UV output. Note the manufacturer recommends replacing bulbs after 4000 hours due to reduced UV output, which I obviously ignored.

Pros: Still on my first bulb after 7 years and with satisfactory UV output. There is some heat produced but much less than a mercury vapor bulb.
Cons: I have no idea what UV index I was putting out when I first bought this thing. If it drops over time, I can't imagine what it started at. I should really be happy my tortoises aren't blind, or seeking martial arts training from a rat somewhere. Also, if the face plate ever falls off the bulb, it might as well be a UV laser.

I'll also note that I intend to get data on other metal halide lights, and I am messing around with LED as well. LED's that put out meaningful amounts of UVB are not available, but they are unmatched in generating high quality, broad spectrum visible light - my main purpose for using them is twofold: First, I want to grow plants in the tortoise enclosures, so I need high intensity visible light of the proper spectrum (measured as photosynthetically available radiation or PAR). Second, I want to see if brighter indoor lighting influences behavior or helps tortoises adapt when transitioned outdoors (e.g. without a period of greatly reduced growth that I normally observe). For reference, the intensity of sunlight at Earth's surface is ~1,000 watts per square meter...

Steve
 

ZEROPILOT

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A SOLARMETER is a great investment.
Your readings are similar to some that I've tested.
Your MVB information is spot on.
I try very hard to discourage their use. Especially since they cost almost the same as a highly superior T5.
My artificial UVB needs are for my trio of Veiled Chameleons.
My tortoises all live outdoors
 
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