If you are up to it, I'd consider either opening up the light and disconnecting the cord where it attaches, or cutting off the plug and getting a new one, and just thread the cord through the conduit without altering the conduit.
I think just spraypainting the conduit (with proper prep work) would look fine. sure, it's vulnerable to scratches (clear coat, or even maybe varnish or something might help...), but in it's position at the back of the tank, it's going to be somewhat sheltered from most activity, and the tank will draw attention away from the pole holding up the light.
Otherwise, something like shrinkwrap, cable organizers, or maybe spary-on plasti-dip (haven't used the spray-on myself) is probably the best intersection of durable and inexpensive.
As to the cable, you might op for vinyl-coated. (or just use grommets). check the random hardware bins in the hardware stores, sometimes you can find little rubber or plastic grommets for various things. Also have tube-ends that might work for the conduit. If nothing else, you might be able to just cut a plug out of wood/plastic/foam/cardboard/whatever, and paint it
Last edited by lochaber; 12-04-2013 at 02:22 AM.
Reason: I swear I'm not illiterate...