Aquarium water parameters fluctuate pretty drastically throughout the day, which can be quite detrimental to the health of your marine life. Temperature and pH both swing up and down based on the time of day, ORP levels vary depending on what equipment is running, and calcium concentrations can be zapped if not properly replenished. These are just a few examples of things that can change over a short time, and all of them can be controlled with an aquarium controller. Just pick the items you want to monitor and control, select the aquarium controller accordingly, and start working towards stability in your reef. As your parameters stabilize, the corals will start to show better coloration, growth, and polyp extension.