Shrimp Hatch??

Ok, last night I was putting in some new coral that I ordered and noticed all at once that there were a million tiny shrimp in the tank. They were everywhere. I was wondering if anyone has had this happen? I had the lights on later than normal so I could see what I was doing, I looked up and they were everywhere. The fish had eaten most of them before I could get a camara to take a picture.

My pepermints have a 'brood' about once a month.  The fish go nuts and stuff themselves to the point of not being able to swim.  It usually happens when I leave my blue lights on till after midnight (wonder if it has to do with resembling a full moon?).  It's pretty cool, but I have no hopes of any surviving until I can set up a sump system.