So, if I were to use these for adding light to my aquarium, which wattage
do I count? The 20 watts the bulb actually uses or the 60 watts it is
equivalent to?

Use the watts the bulb actually uses.

When planted tank folk talk wattages, they are almost always talking
flourescent wattages.

Incandescent light is much less efficient than flourescent, so no one uses
incandescent light, or incandescent light equivalents, for planted tanks.


Leigh

http://www.fortunecity.com/lavender/halloween/881/