Being able to tell if your corals are getting too much or too little light can be tricky. The best way to tell is by the change in the coloration of your coral. If your coral begins to lighten or even bleach, chances are your coral is getting too much light. If your corals on the other hand are browning out and have poor coloration, you might want to try moving up your corals or increasing your light intensity. If corals do not receive enough light, they often grow and a slower rate as well.