Water usage is a big concern for many saltwater aquarium hobbyists. With huge water changes, inefficient RO/DI units, and constant topping off of evaporated water, the average reef aquarium can go through a hundred gallons of water or more per month. The major source of waste is probably going to be the reverse osmosis water purification system, as they typically produce two or three gallons of waste water per one gallon of usable water. To cut these numbers down a little, a booster pump can be added to the system, and any waste water can be used to water plants or keep the grass damp. These two uses for RO/DI waste water are particularly important this time of year, when the temperatures are at or approaching their peak, and rain is scarce in many areas.