To Cycle: Add at least one or two bunches of plants to your tank. Stock no more than 1" of slim bodied fish per ten gallons of water. Test nitrite and ammonia daily. At the first sign of measurable nitrite perform daily 50% water changes with heavy vacuuming. Continue daily 50% water changes until nitrite is no longer measurable. Once unmeasurable your tank is cycled. Your fish are still doing great because ammonia remained unmeasurable and nitrite was only at trace levels.
Always add plants as they prefer and will consume ammonia over nitrite and nitrate. Stock low to keep bioload from overloading. The daily 50% water changes along with heavy vacuuming not only keep the nitrite level in check, they also keep the bioload in check while the nitrite cycle completes. Why didn't I mention water changing during measurable ammonia, you ask? 'Cause you most likely will never encounter any measurable ammonia.
The primary reason for cycle failures even among the cycle aware is way overstocking for the process. It becomes impossible to keep up with the bioload. Ammonia and nitrite spike out of control, the tank ends up clouding over, and/or fish die. Additionally, the value of even just a few plants goes highly underestimated by far too many. We just don't see it enough in cycling info. Plants drink ammonia like mad and if the tank is stocked lowly even just a few plants will prevent any measurable ammonia from appearing. The ammonia phase of nitrification occurs invisibly with the only sign of it being the emergence of measurable nitrite.
Painless fish cycling that even the beginner can easily perform.