Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Dirt, plant and monitor.
Some garden soil will go through its own cycle. The natural microorganisms in the dirt may or may not live under water, and it can take up to a month for them to sort out who is living and who is dying.
You can begin the fishless cycle when you start the tank, but a few things to watch for:
1) Many plants do not like high ammonia. You might want to test twice a day, and add as needed, but ONLY to 1 ppm ammonia. This is still a lot of ammonia, but is spread out over the course of the day so there is no one peak that is too high for the plants.
2) Test Test Test... the newly submerged soil might produce enough (or even too much) ammonia all by itself. You might not need to add any for a while. As it settles into life underwater, you may find that you will need to add ammonia later on in the cycle.
3) If the plants are OK with a bit more ammonia, the nitrifying bacteria are OK with ammonia to 5 ppm and nitrite to 5 ppm. However, if the ammonia is constantly returned to 5 ppm then the nitrite production will go too high, too fast. Best: Add ammonia to test 5 ppm only a few times, just in the first few days. As soon as nitrite shows up allow the ammonia to drop to 3 ppm, and maintain it there for the rest of the cycle testing and adding ammonia once a day. If the plants have trouble with this much ammonia, revert to hint number 1.
4) Be patient and give it time. A whole new ecosystem is developing, and this does not happen overnight.