Will pond filter bacteria colonise without fish?

It needs ammonia that can come from fish, fish food, or pure ammonia. For ponds, the easiest thing is to very lightly stock your pond at first. Only add a few fish and give the pond several weeks to start maturing. During this time, the bacterial colony in your filter will be growing with the ammonia and you will start to get a good culture of bacteria capable of processing the biological waste. After a few weeks, you can add a few more fish, and so on.