The bulb is a GE F15T8 SP35. Since it's not sold as a specialty bulb it doesn't cost much. GE publishes the wavelength spectrum for the different phosphor coatings used in their bulbs. This one as well as several others put out into the UV spectrum and the output graph seems to match very well with the higher cost specialty bulbs sold for UV.

It's the last four alphanumerics in the bulb code that tell you the phosphor type in GE's linear fluorescent tubes. SP35 in the case of the bulb I'm using. You can find GE bulbs in other sizes that use this same phosphor coating.

Though I will admit the cost of specialty UV bulbs for amphibians has come down, but still it goads me to pay extra just because they put a picture of an amphibian on the box. As far as I know fluorescent bulbs naturally produce a lot of UV. Its the type of phosphor coating used that determines how much UV escapes. Some allow none to get out and convert it all to visible light.