unknown eggs

[vanillagorila]

I am currently in between tanks right now and I have moved all of my livestock to a small 20g temporary tank set up. I have a pair of clowns, a pink spot watchman goby and a single Banggai cardinal. My only guess is that they came from the Banggai. They are about the size of a dime across.

 

[vanillagorila]

After a few google searches it looks like these eggs are from my Banggai. I guess, now I know that I have a female, but I wonder why she would lay eggs without a male around.