Hi Wayne
Have you tried to Airlift the eggs out,if not make one out of a lenth of electrical condute shape it in very hot water like a walking stick,elastic band a silk stocking on the bend to catch the eggs. cable tie 6mm tubing from airpump to the other end - keep the bottom end close to the bottom so you dont accidentaly suck up one of the smaller koi's.The total length must be as such that the top of the bend is on the water line.
Have a look at the wife's washing machine discharge outlet maybe you could use that.
Hope this help.