I usually keep what I call a 'Junk Tank'. I don't quarantine my fish, so maybe if I had a quarantine tank it would be the Junk Tank.
These reason for a Junk Tank is have a place to dump things that need to stay wet. In mine I have:
plants I never got around to planting
spare snails
extra mulm
Apistogramma eggs
I have a pair of Apistogramma nijsenni in a crowded 40 gallon breeder (with no filter and rare water changes for the 'how many filters do I need in X gallons crowd') that spawn relentlessly. Of course the fry don't make because they get eaten by the all the swordtails, zebra danios, sparking gouramis, and guppies.
But on a whim I dropped the breeding coconut shell where mom always lays her eggs in the Junk Tank. Problem was I couldn't see them.
I think I may have solved the problem with this thing, the 'Flipper', which is a magnifying glass with a double magnet on it.
Here is what it looks like looking through the Flipper.
I can now see the little red eggs.