what kind of shrimp? if you have any saddled females (can see green or yellow eggs developing inside her in the form of a saddle behind her head) when the eggs are mature enough, they will molt, then hide and send out pheremones signaling males to come mate, after they mate, they eggs will be laid and stuck onto the underside of her tail, it takes about 3 weeks for the saddled eggs to mature, and another 3-4 for the eggs to hatch, so its about a month cycle as a female will usually develop her saddle while she is berried (has eggs underneath) good luck! and i hope you have babies soon! also, if you want to sex the shrimp, the best way is to look @ them from the side, the underside of a females dail will have a downward arch, which is where she puts the eggs, whereas a males tail will be narrower when viewed from the side, and will go straight across the bottom.