I may have not been clear, I do not have my small containers in the system. One container is inside of my basement window and the other is outside of the basement window. The one outside is the one i am using the pond water in. i hope that takes off and i can harvest that to supplement the one inside as right now both are rather small trial setups. I just use fish tank water to replenish the one inside. Bsfman, do the duckweed need a high ammonia level? Or is that just a convenient place for relief?