Convicts are easy. Way before I knew about them I bought one and had it in a 30 gal hexagon. I was reading a book and they talked about cichlids and said female convicts will have like a brick red color on their belly. I looked at mine and it had that on its belly, so I knew I had a female. Not really after long since I bought it, I noticed eggs on the bottom of the tank. I was excited but doubted they would hatch.
But I know some fish can save sperm and have fertile eggs without having to engage with a male each time. But the eggs disappeared one day because they were no good.