I had three once a few years ago and I had no trouble from them,they were quite docile most of the time.
They just hang around the surface moving slowly until feeding time then they soon come alive.
I have read reports of people saying they become nasty with each other but this was not my experience of them.
I would not be concerned over them preying on your corydoras, your geos are more likely to do that.
Word of warning, cichlids can die trying to eat corydoras, I would change them for Brochis if you can. They are a lot bigger and a safer bet.