Size matters, and since you won't get your amanos to breed you don't have to worry about baby shrimp. The adults normally would be fine with what you
A stab in the dark here, but I remember coming across something like this before in my reading. I think it is a kind of Long Arm Shrimp, Macrobrachium
Red hooks will develop irregular spots of red and black when they're ready to spawn, look downright diseased compared to their usual silver display.