Hi shark. The roots of the plants act as the filtration system and remove all three forms of nitrogen and anything else chemical wise that might harm the fish. By simply feeding the fish, they'll provide all the nutrients the plant requires to be healthy. By replacing the water lost to evaporation (the tank is open to accommodate the plant) with distilled water, you're not overloading the system with more minerals, since distilled water has none. The system is self sustaining except for feeding the fish every day or two.
10 Tanks