It certainly wont harm them however 18000k is lopsided in the color spectrum in that the plants will be using mostly blue side of it. I think the bluer end of the spectrum would look great in a planted tank but im just not sure that youll get the same growth as you would from a bulb in the 5000-10000 range.
There isnt anything you cant find on the net if you search around.
Birthday is around the corner.. I may get my wife to buy me a single strip t5ho and move the power glo bulb to that one and get a second lifeglo bulb or something of that nature then. If I'm gonna go with the escondido's that bluer bulb will really make the fish look much better.