my experiences:
1st tank : 34L - added 2 guppies , got ammonia readings, went through cycle, added a couple of fish every week or so.
2nd tank: 20L - added JBL filter start and one bristle nose.. never got any ammonia or nitrite readings at all. Added a fighter a couple of weeks later. That tank must have had a super fast cycle because i tested every day and never got ammonia or nitrite readings.. can only reason that it cycled within hours between my tests... anyway, I'm convinced the JBL filter start did a really good job. It's a little bottle that you add the whole thing to the filter. BNs are messey fish too!
3rd tank: 160L - used all the media from the 34L and kept same number of fish. no need to cycle. Added a couple more fish every week or so. No spikes that i know of. (this is the tank with your ottos sophia!)
restated 34L tank - used 4 guppies to cycle- got the usual readings
4th tank: 70L - used the media from the 34L tank again and put the guppies in new tank. so far so good.
conclusion - use existing /seeded media if you can .. otherwise JBL filter start was really good. With ALL my tanks I also use TLC once a week when first starting up and then every time I clean the filter or change the wool. The bottle says to add it weekly but I don't think that is necessary.