Maintenance is critical in any saltwater tank.  I perform 20% water changes on my tanks every 2 - 4 weeks.   Changing water keeps the water in the system fresh, removes unwanted wastes, and adds vital minerals to the system.  Most aquarium salt contains trace minerals, and with frequent water changes, your fish and invertebrates will get what they need to thrive!  My filters are also rinsed out or replaced at this time.  When necessary, I will remove some of the gravel in the aquarium in order to give it a thorough cleaning.  I do this with a piece of plastic tubing, about 1" in diameter.  Start a siphon, and suck the gravel into a bucket!  Rinse it thoroughly with water, and return it to the tank!   This removes detritus, waste, algae, uneaten food, and other unwanted junk that settles at the bottom.  Periodic cleaning of the aquarium's glass, and that's about it!  Not as hard as everyone told me it would be!  Then again, everyone that told me that never had a saltwater aquarium, either!