Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Nitrifying bacteria thrive in high oxygen. They might even demand more oxygen in the tank than the fish.
Monitor the ammonia and nitrite levels. Keep them no higher than 5 ppm. The bacteria do not grow so well when the levels are higher. If you need to do a water change to reduce the levels it is just fine to do a really big one and drop the levels way down, like under 1 ppm. The soil will add the ammonia right back, and the ammonia-to-nitrite bacteria will be converting it into plenty of nitrite for the next group.
The only problem I see is if the substrate does not contribute enough ammonia. Then you might have to add some. Look for non-sudsing, no surfactant, no perfume, no fragrance type of ammonia. Probably available in hardware stores, Dollar Tree sorts of places and perhaps the grocery store. If you need to go this route add just enough ammonia to raise the level to 3 ppm once a day. It will drop overnight, then add more the next day.
Occasionally do not add ammonia and see what the soil is doing. It may still be contributing a bit more ammonia than the bacteria can use.
A fishless cycle, starting with no bacteria takes 3 weeks.
Since the soil may continue to leach ammonia for a month or more, this ought to be plenty, but toward the end there may not be very much ammonia from the soil to keep the bacteria fed.
Another possible problem: Some of these substrates remove the carbonates from the water. The bacteria need carbonates. This is their source of carbon. Keep the KH not lower than 3 German degrees of hardness.