gazjoo

The more fertilizer (or goldfish) the more water movement you want. The airstones used in a fishtank add oxygen because they create a flow of water from the bottom to the surface (as someone else mentioned, thats where the oxygen enters the water) but anything to move the water around. Running water doesn't have less bacteria (probably more) just different types of bacteria. Aerobic bacteria intsead of anaerobic. These are good bacteria for a pond system as it is these bacteria which break down fish wastes, rotting leaves (organic matter) etc. into plant nutrients.