I will stick up for fishless cycling here as I believe it is a ethical way to ready a tank for shrimp or fish without intentionally exposing shrimp or fish to high levels of ammonia, which as we all know is bad for them.
Fishless cycling can work to establish the bacterial colonies that consume ammonia and nitrite. However there must be a source of ammonia - fishfood, rotting meat, plain old ammonia itself. The point is to establish the bacterial colonies using your ammonia source, then add your livestock so that they provide the ammonia (and of course stop adding the original source of ammonia). The number of bacteria will either shrink or grow to account for the differences in the amount of ammonia you fed the tank verses how much the fish produce. Bacteria reproduce extremely quickly, minutes to hours. And remember that their number grows exponentially - 1 becomes 2, 2 becomes 4, 4 becomes 8, 8 becomes 16, 16 becomes 32, 32 becomes 64. And so on.
Just to reiterate - fishless cycling is designed to ensure that the bacteria are established in the tank. It is not designed to perfectly match the number of bacteria to the amount of ammonia that will be produced by the fish that will be added. As explained above, the bacteria will quickly adjust their numbers to account for any differences in the amount of ammonia (and nitrite).
The amount of bacteria in a tank never remains constant. It fluctuates to account for the amount of food (ammonia, or nitrite) is available. More fish = more ammonia = more bacteria. And vice versa of course! If you feed the tank, there will be a increase in the number of bacteria as they consume the ammonia produced via the feeding fish, then over the next few hours their numbers may decline as the amount of ammonia in the tank decreases.
That said, I believe the best method is to add established media from another tank to introduce the bacteria into a new tank, and as I mentioned above, they can rapidly reproduce to use up all the available ammonia (and nitrite) so fish or shrimp are never exposed to high levels of ammonia. If you cant do this, fishless cycling or other methods that prevent the exposure of organisms to high ammonia levels are in my opinion the most ethical ways to cycle a new tank.