Hello, I am planning to get a meter to measure the UV output of my bulb. I am aware that the solar meter and zoo med brands are basically the same thing. But I'm a little confused as to the 6.2 and 6.5 models. I've heard that Tortoise owners are starting to prefer the 6.5 UV index model, is that true? I am also having a little trouble finding that model. Where can I get one? Any information would be greatly appreciated. Thank you.