The nitrification process or nitrogen cycle is a biological process that changes ammonia (NH3) to nitrite (NO2), and then to nitrate (NO3). To do a fishless cycle you add the ammonia to the pond daily to begin and maintain the process. The other option is to get a few fish instead but until the process completes, about six weeks, the fish will be under stress due to elevated levels or first ammonia, then nitrite.
Get a pond test kit to monitor ammonia, nitrite and pH. Additionally it’s a good idea to also monitor KH (hardness) as the bacteria need and will slowly deplete hardness.
The advantage of the fishless cycle is apparent if you are purchasing expensive fish. Say for example you want to purchase larger shubunkins locally or mail order. If you are happy with “feeder” goldfish then fine but be aware a lot of the local pet stores feeder fish are already sick before you purchase them. I’ve purchased some from local PetCo and they’ve been perfectly fine but it’s always a crap shoot. If you have a good pond store that has shubunkin and comets and are happy with smaller ones to start than 2 or 3 will probably be ok. The advantage of the fishless cycle is not stress the fish and risking loss, the disadvantage is that it will take about 6 weeks (with or w/o fish) to complete.
Some companies sell nitrifying bacteria but it doesn’t really work. The only way to jump start the process is to get living bacteria from active biological filter media where they are concentrated from another pond or aquarium but you also risk getting whatever disease those systems have.
