I have a fully planted 75 gal tank. I have 4 axolotls in it, and about 20 Amano shrimp.
I recently added 15, because 5 were left over from 2 years ago when they were born in there from the parents I bought the first time I added them (when the tank wasn't nearly so grown in with plants and I had 3 axolotls)
I find, that if they survive the first 10 minutes and do not swim, disoriented, directly into an axolotls mouth, (as they do when first introduced) they establish little territories in safe, planted, and hard-to access areas.
As long as the tank is somewhat vast and labyrinthine, They seem to rarely become food. And if the numbers are high, it makes a noticeable difference in the algae. especially on the plant leaves which can compete much better with the shrimp to eat the algae.
It's okay if they get eaten. Generally, they don't.