I have heard the shells are not good for fish, but don't know for sure
I have been using these mini-hatcheries (from Brine-Shrimp Direct, where eggs are sprinkled around the edges, and the top has a hole in the middle where light enters in that small area. The newly hatched gravitate toward the light, where a little scouper is sitting.
lift the scooper full of artemis, feed and put back, the egg shells are left around the side.. after a couple days
I throw the hatched (and unhatched) eggs, and salty water outside into a pan where many still hatch over timeand the algae feeds some to adulthood