And this is why I ask first. Thanks!Nooooooo! Fools gold has iron and sulfur in it. These would be very bad for your fish.
You are just smarter than some of us by asking first rather than later after a few fish deaths.
I was wondering would it be possible to coat it in a clear aquarium safe coat? I can't remember the name but I heard people coat certain things to make them safe for their tanks.
I don't think so all the pics I've seen pics where people seal things and they always look amazing. And if it happens to ruin it at least you tried lol
You could always try it on another rock maybe something that looks similar just to see the effect.