Over the last couple of days a rapidly spreading, light brown color has been spreading in my tank. The only recent change I've made is a few days ago I added a light to the aquarium. I've been keeping the light on all day and turning it off at night. Note. the coloration is only on the decor and plants, not the glass sides. Could the added light be promoting some kind of algae growth? If so, is it dangerous to my fish?