I like the idea of the Christmas lights. They are cheap and you can get extras around the holidays to last a whole year in case of problems.
I was wondering if a rope light would be safer though. Water splashing on the light bulbs could be a bad thing (I work on electronic equipment and I have a thing against water and electricity)or, if you have a barrier between the lights and water, the water vapor could cause the light connections to become corroded, causing the lights to fail.
Just wondering... I tend to point out possible problem areas. Sorry, it's a habit from my job.
edit: nice job on the tank!