Minnow Eggs?

[shoelessdan]

I have a 15 gallon tank with 12 minnows in it, i believe that 4 are male, and 8 are female. Would it be hard to find the eggs? And how do you know if one of the females are about to have eggs?

To help show you what kind of structures i have in the tank, here are some pics, hopefully you can help me figure out where could be a likely spot,or if i should add something:









Thanks alot in advance