I am sure the question has been asked before but I couldnt find anything searching for 18" bulbs. I have a newly RE-planted 15 gallon tank. I learned the first time around 'stock' light just doesnt cut it. I am here to ask for the BEST bulb I could buy in the 18" setting. Only thing I can find is the 24" and up size bulbs! Any and all help is appreciated if someone can steer me in the right direction. I am thinkg 1-2 wpg is more than enough also. Thanks!