Stable and high-quality water in your aquaponics system starts with a clean, fresh source. With commercial systems requiring tens to hundreds of thousands of gallons, this is trickier than you might think. Ponds, streams and rivers are often available near the facility, but even the cleanest of these usually supply water with one or more serious quality issues. Even wells can produce water that is out of pH balance, and public water supplies often contain compounds like chlorine that can harm the fish.

Even in recirculating systems, like most aquaponics designs, you must add one percent of the total system volume every day to compensate for evaporation. Not only will you need a source for the large filling required at the start, you’ll need a way to keep adding a few dozen gallons here and there. The following water sources are ranked from best to worst. They include notes on what to look for during testing and how to prepare the water for use in aquaponics.

Wells and springs: Because both of these features are producing water filtered by many layers of soil and rock, they tend to offer the highest water quality. You still must check for pH, as filtering through layers of rock tends to dissolve minerals like calcium that buffer the water and make it harder to adjust. Dissolved gases also tend to be high in these sources, but all the gasses common to spring and well water tend to evaporate rapidly with agitation. Temperature is usually constant with these sources, making it easier to pump directly into the system.

Rivers, creeks, streams, ponds, and lakes: Due to being open to the air and full of living creatures, including fish, these sources tend to be higher in contaminants and unwanted nutrients. Using this water in aquaponics may lead to nutrient overloading that wouldn’t occur in hydroponics without the fish component. For many rural areas where water rights can be secured, this is often the only available water source. Extensive filtering and treatment may be needed to prepare the water to enter a closed loop system. So, you may need to set up multiple tanks just for daily processing of the replacement supply.

Municipal water: While drinking water from a municipal supply is often the highest-quality water available in an area, it’s also very expensive. Filling up a commercial system for the first time can cost hundreds of dollars and refills continue to add a monthly operation cost. There are still a lot of chemicals and compounds either not removed from the water, or added to it on purpose such as chlorine and the chloramines, that can harm both fish and plants. Look for alternatives before connecting the system to your local municipal water supply.