I am old, and started keeping fishes before such bacteria in a bottle product's existed.
I and other's, started our community tank's by setting them up,plug in the charcoal filter,heater, and let the tank run for a week to ten day's.
We then selected very small ,hardy fish ,and very few, (tetra size) and placed maybe three or four of these fish for let's say 30 gal tank.
We fed the fish tiny amount of food perhap's every other day for approx ten day's.
These small,active fish, represented a very small bio-load on young tank, and with sparse feeding's, and not too many fish ,or two large of fish..there was no harm to the fishes.
After ten day's from first three or four fish,,we added another three or four tetra's,small barb's,danio's, and continued to feed tiny amount of food every other day and after another ten day's,, we then performed first water change ( around three week mark) and maybe selected a group of four to five cory's, or other tetra like fishes if bottom feeder's were not desired, and continued to feed small amount and after the fifth week ,maybe select a centerpiece fish such as Pearl gourami ,or Honey gourami.
No daily testing was needed,no daily dosing of ammonia,no daily water changes,and the tank's were allowed to mature slowly,gradually, without harming the fishes.
I appreciate that thing's have advanced, but new hobbyist's are often taken in by the label's that say.. Add this bottle of #$*!*! and add fish same day.
They do not understand, that this does not mean you can add all of the fish in one go,(even DR, Tim rightly point's this out) and problem's arise quite quickly,(sick ,dead fish) depending on number's of fish,food's offered,and volume of water.
These product's at best,,allow for what could be done without the product, with a little bit of patience,discipline (short supply these day's).
I... as stated previously,,, wished these product's worked well for everyone, but the simple truth of the matter is,, that they don't for various reason's, not all of which are self inflicted.