Wh start with so many? where will the go once they breed?
I'd say start with 25-40. Grow them hearty, establish them, and then let them breed. What's the enjoyment of a ZOO without watching life and breeding take place?
I am in the same situation. I have a new 10 gal that I will plant in a week. My first purchase of shrimp will be 10. With Red Cherries I had 3 varieties before I got a male to mate with a female. and I had 7 BEAUTIFUL, thick, and gorgeously coloured females. Time told great things!
I think 150, even 50 at the beginning would be overkill. Mine were 1.5" long and were well treated. I had 7, then bred, and I had 21.
Also, are you planting the tank?
They love simple plants like java fern and vals to nibble on.
It's a beautiful process.
So m uch so this tank will have nothing but shrimp and khulis!