Strange pink rock?

So this is week 2.5 of my first SW tank. It is a 5 gal tank with HOB filter and top fin power head. Live rock and live sand installed day 1. Ammonia levels are around 0.3 ppm, nitrites are 5.0 ppm, and nitrates are 50 ppm. I think I'm on the down side of the cycle, as the ammonia has been slowly dropping.

So this morning, everything was normal in the tank. After returning from work this evening, there is a small (almost sand grain sized) pink colored rock in the middle of the tank. The picture is bad, but the rock is vivid pink; and when the light is turned off, it is still pink.



Does anybody have a clue as to what this might be? No one touched the tank while I was gone, so it originated from the tank. Do I have a rare coral that magically started to grow in my tank? Some type of critter?

Thanks for the help!