I have a 20gal tank with 1.5wpg on it, I'd like to know what are the effects
on the tank if the lights are left on for 14+ hours a day?

Algae. Fourteen hours is okay, but if you go much longer than that, you may
have an algae problem.

Fish need a day-night cycle, too, so it's not good for them to leave the lights
on all the time.


Leigh

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