UV glass...

[midgetwaiter]

Regular old plate glass will block dangerous UV wavelengths. 100% of UVC, 99% of UVB and about 60% of UVA. In this case, longer wavelengths penetrate better. I know this is runs contrary to the what most people have to say but I spent a few years working in an industry that relies on UV light (indoor tanning) so I have some detailed experience.

So unless you do something odd like stare at it for 20 minutes that much UVA is not going to hurt you and will be blocked at the water's surface, protecting your animals.

The one thing you might get from a specialized glass is the ability to handle the heat better. A Laminated glass may be the thing to use here, it might still crack if splashed but wouldn't explode like plate glass.

http://www.newton.dep.anl.gov/askasc.../chem00539.htm

http://en.wikipedia.org/wiki/Ultraviolet