Ultraviolet light does it to vinyl in about a month. What I do with my overly stiff tubing is snip off the part causing the problem, then splice in a fresh piece. The stuff away from the lights seems to last for years.
SYLVANIA 2-Pack 60-Watt Equivalent Daylight Compact Fluorescent Light Bulb 1.5" diameter, 3.75" length
SYLVANIA 2-Pack 100-Watt Equivalent Daylight Compact Fluorescent Light Bulb 2.25 diameter, 4.25" length
Not so certain about the 100 watt equivalent fitting.
GE bulbs are about .25" to .5"...
Keep in mind you have to have about 12" above the rim of the tank for cleaning, otherwise it is awkward. If you don't have 28" or more, regardless of lighting choice, it will be a pain in the butt.