Definitely not an easy genus of fish to care for (there are quite a few species labelled as "Elephant Nose Fish" with G. petersii being very common), should be kept in groups of 6+ and will need a big tank at least 6x2x2. Options are extremely limited when it comes to using medication and they will not tolerate anything but absolutely top water quality.
They get to around 9/10" in the aquarium apparently. A type of Mormyrid, hence when you see some medications saying "do not use with mormyrids" that'll be the one! As for the 6+ I heard it was either one.. or 6+ just because of the stronger ones bullying weaker ones.