No idea on the gestation period, but be aware of the below (from www.petshrimp.com).
larvae go through several planktonic stages before metamorphosing into post-larvae (miniature shrimp) and assuming a benthic lifestyle. For this process they need brackish water to full strength saltwater.
There are documented cases of successful Amano shrimp breeding online. There's also a user here, palacan, that has also had success breeding Amano shrimp.
yeah, i know they need brackish to salt for the larvae, I'd just like to know how much time I have.. I picked up the salt the other day, but I don't have a hydrometer yet..
Just kinda wondering if I was looking at DAYS or WEEKS.
You'll also need marine green water to feed the larva.
Do you know how long ago the eggs were laid? In general, it takes approximately 30 to 40 days, depending on water temperature, for my shrimp eggs to hatch. That may give you an approximation, however, I don't breed any lower order shrimp (shrimp that require marine, or brackish water to mature from larva to shrimp).