My pepperment shrimp have had baby's twice, that is probably what you saw. They have the baby's at nite , usually around 12pm, don't know why at that time ,but thats what I read about them and it is true. Looks like a snow storm, it only last's a few min. but it's cool to see! I also read that it is almost impossible to raise them due to their size. The hard part being feeding them.