Over time, the pH levels on our tanks has a tendency to drift downward. A day or two before you start any big maintenance jobs on your tank, check the pH and slowly adjust it back up to where it belongs (8.0 to 8.2). This will help avoid pH shock to your tank critters.
This is also a good time to take a hard look at your system components. If your light bulbs (fluorescent, PC or MH) are over 9 months old, it is probably time to change them. Replacement bulbs are not cheap. You might want to take a serious look at upgrading your lights to LED's. Financially, LED Lighting on Your Reef Tank really makes a lot of sense. The LED's might cost a bit more that PC's, fluorescents ot Metal Halides, but the cost savings (much lower electricity consumption and much longer bulb life) of LED's over time are terrific.
While you are at it, you might want to give some serious thought to reducing some of your routine maintenance tasks with a little forward thinking. Nitrate control is a major problem for many people with reef tanks. Take a look at the Vodka (ethanol) Method for nitrate control. If you are performing one water change after another just to keep your nitrate and phosphate levels in check, adding a little vodka to your tank twice per week can save you a lot of time and the money for sea salts. If you use water changes to balance your calcium and trace minerals, periodically dosing your tank with a good calcium supplement, many of which also contain the trace minerals your reef tank has depleted will also save time and money.