The apple snails do fine with other snails. They are a wonderful addition to an invert tank. The shrimp reproduce quite readily once they hit sexual maturity. Once you see the visible saddle on the females (a patch just behind their head that is yellow or greenish in color) it will be 2-3 weeks until they are berried (carrying eggs) then another 2-3 weeks until the eggs hatch. There are typically around 20-30 young per female. This adds up fast! Congrats!