Koi Spawning

My Koi appear to be spawning. I've never noticed this behavior before
as they were probably too young. I found clear small balls floating on
the top of the pond in clumps. I removed them the second time I saw
them to a separate container (the first time I left them and they
appeared to be eaten). Are these fertilized eggs, or did I remove them
to soon? How do you know the difference between fertilized and
non-fertilized eggs?