And/Or just plant heavily as plants are covered in biofilm. Right?
What makes plants beneficial for "cycling" is that they eat up ammonia and nitrite. Over time, biofilm develops, and they play there role in providing additional surface area for bacteria (which also grow over time).
If they are healthy and growing, the NH3/NO2 reduction can be instantaneous.
Always, always a good idea to add your bioload (fish) gradually, over time.