The koi angels, Robert Redfish and Susan Saranfish, are having difficulty grasping this whole concept of hatching eggs and caring for young.
When the parents don't have the instinct or the experience to fan the eggs, fungus forms. When that goes unchecked, the eggs will not hatch and instead, the fungus will just continue to grow.
This is what has happened with Robert and Susan.
In the picture at right, the eggs have fallen from the arch due to the weight of the fungus. It's the white "stuff" you see in the corner of the picture - and if you look closely, it's also on the snail, who is probably loving this protein-rich meal.
I can do a regular water change, in which I can place the suction hose directly atop the fungus and eggs to suck them up and away. Or, if there were only a few, I can use a turkey baster to suck them up. (Of course, the baster is ONLY used for the fish tanks - no need to avoid my house on Thanksgiving Day!)
Because Robert and Susan have laid eggs multiple times, they will continue to lay them. Eventually, they will figure it out and at some point, the eggs will begin to be taken care of properly (we hope).