can i put a derasa with my ilumination?

i have a 30 gal tank with a 70w MH and 60w of actinic NO. i was thinking in putting a small derasa or squamosa on the top of the tank, about 15 cm of the surface. what do you think about it? i put bio calcium in the tank and my alkalinity its ok, and so is my calcium. i dose iodine every week