You set up your tank, buy some shiny new lights, plug them into timers and then wait… how long should they be on? What will match your routine? What about the health of your reef? Fish and corals in nature are very aware of the daily cycle, so much so that if you purchase a wrasse from another part of the earth, it will still be on that schedule. I’ve purchased wrasses in the past that stayed in the sandbed way longer than expected, emerging hours after the lights came on because their internal clock was still calibrated to the previous time zone. After a couple of weeks, it would reset so precisely that it would circle and hover over the perfect spot mere seconds before the lights shut off. Pretty fascinating to watch, I have to tell you.If you have a simple system with T5 bulbs, your options may be limited to how many bulbs you can turn on at a time MORE: That perfect lighting schedule – what you need to know