Water changes are a task we rarely relish. Some swear by them, and others do them sporadically throughout the year. While water changing philosophies vary from hobbyist to hobbyist, the bottom line is that water changes can benefit your livestock. They are the easiest way to improve water quality and also are one of the most inexpensive solutions when trying to solve a chemistry problem in the system.
For nitrate and phoshpate control, I'm using a NextReef reactor. Model SMR1 XL, this reactor holds 2 liters of Vertex NP biopellets. Plumbed to the manifold, a ball valve is used to control the flow rate through the pellets. I've been running biopellets since February 6, 2011, and it appears to be working well: water-testing
When keeping an aquarium, the best husbandry requires owning and using test kits to measure water parameters. Most kits have enough tests to last a full year, and using these kits frequently assures happy livestock. If a kit has 50 tests, that's an indicator it should be used weekly. I'd recommend that kits be replaced annually. Mark the date on the box when you purchase it and open it for the first time to avoid relying on a dated kit. Older reagents may lead to false readings.