You can add forage like fathead minnows as soon as the water is more than a foot deep. Bugs and other small critters will be immediately drawn to the water, and zooplankton will fire right up like magic that the FHM will feed on. It is actually a pretty amazing process to watch.
Then next spring, things will really fire up! Give the forage a year to populate to the point of being able to walk across their backs, and you will be ready to go. Be sure to follow recommendations here to give your pond a boost at the start like proper fertilization to get the biology off to a good start.
