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Steve reminded me that I had a question about this.

I have seen it suggested that if you can get them out for an hour 5 days a week in the sun that a separate lamp would not be necessary?

What are your opinions?

I mean, I know it doesn't shine all the time, but I AM in Houston. I also don't notice Izzy basking a lot when she is outside, she would rather hide under her platform.

Also, I have seen mention of the mercury (something) bulb. I have a 55 gallon... would that be beneficial for her more than getting another UV lamp?

I don't know about the length of time in the sun, but I just recently changed over to a 100w mercury vapor bulb. I used to use a seperate basking heat lamp and a 5.0 compcat florecent UVB bulb. We had eye issues with the compact and the two seperate lights were kind of a pain. I set the MVB 12" from his basking platform and he's been basking under it like crazy. No problems with his eyes, and it even looks like he might finally be ready to shed his shutes! I've got a 75 gallon tank, but I have been told the MVB is OK for anything over 50 gallons.

The UVB is real strong during the summer, I think an hour might be too much heat (depending on the outdoor enclosure). You will get some UV on cloudy days too, even a bit in the shade. The UV is substantially greater compared to florescent bulbs.

If you get them out several times a week in unfiltered sunlight on a regular basis, it is possible to meet their UVB needs. Forty-five minutes to an hour should be fine.

If it's really warm out, I'd be more concerned about them overheating than getting too much UVB rays. When my turtles are out on sunny days in stock tanks, they will bask for hours (especially my RES). If it's too warm, though, they tend to bask for shorter periods or stay in the water where it's cooler.