well, what else is in the tank? the eggs will only be fertile if a male fish fertilized them.
generally speaking, however, infertile eggs will have a "milky" look to them and will shortly be eaten by the parents (no sense in wasting good protein )
if it turns white its bad if it says a translucent color than its fertile. In a few days if you noticed that they are eating the eggs you know that they are bad.