swc=shallow water container If you have beneficial bacteria growing you should not have to change water. I've been running lettuce in a swc with hydroton rocks to hold the beneficial bacteria. I have not changed the water yet. It's been two months. I only have about 1 1/2 inches of water in the container. I don't have any mj beans so I am forced to experiment on veggies till I can get some.
I can tell you the lettuce is beautiful and delicious.