Eggs CAN be removed from the nest right after spawning if it's done carefully. Here is some info from Bettatalk about how to remove eggs after spawning. The eggs are removed right away, before they have a chance to develop into babies.
So here is how to remove the eggs, step by step:
first of all, once the spawning is done, use a flashlight to see where the eggs have been stored inside the nest. They may be all over, or clumped in one or two spots. They are easy to see since they look a bit yellowish. Look at them from UNDER.
now, remove the female.
while you are in there, this is the best time to also remove extra eggs - this way you only disturbed the male once.
take a clean plastic spoon
carefully dip the spoon near the nest by entering the water surface vertically (so to displace almost no water). Slowly maneuver the spoon under the nest. Level the spoon so it is horizontal and slide it slowly under the spot with most eggs. Scoop up bubbles and the eggs, keeping the spoon mainly horizontal but at a slight bit of an angle when exiting at the surface so to not displace much water at all (it will disrupt the nest less that way) but so the eggs you scooped up will still not fall back into the water.
if the nest is under a stirofoam cup, you will have to lift the cup up gently so to access the eggs and remove them. This will result in the nest sliding partly out, but that is OK. Remove the eggs, then lower the cup back into the water while trying to move it over the majority of the nest and getting as much of it back under the cup - the male will fix the rest.