The nitrogen cycle uses up Carbonate Hardness (KH
) in the process of turning ammonia into nitrate. 7ppm KH
is needed to process out 1ppm ammonia. When KH
is gone 2 things happen.
- The nitrogen cycle no longer functions.
- The buffering capacity of the water disappears and the other natural processes which acidify the water can no longer be absorbed and you see a pH crash.
In normal circumstances regular water changes, even with soft water, will replenish KH
and stop this happening. If you are finding the KH
in your tap water isnt enough to do this you may have to intervene with a source of KH
Sodium Bicarbonate is a KH
source. Other ways to add KH
is a piece of cuttlefish bone in your filter or aquascape or a bag of crushed coral in your filter.