I was never successful keeping them as a single individual FM, in a mixed cichlid community situation, there always seemed to be ongoing problems, especially when kept with more obviously aggressive cichlids.
After learning the best way to keep them, was in a single species tank, as a shoal, (the way they live in nature), not only for Thorichthys but other similar earth eater types like Cribroheros, and most Geophagines, they did so much better , and exhibited much more interesting behaviour.
For example from much of the literature, it seemed common knowledge that when Cribroheros rostratus was kept as a single individual, they tended to be either hyper aggressive, often destroying other tank mates, or painfully shy, and they are a very similar earth eating species to the FM.
So when I had a chance get some, I bought a group of about a dozen, and grew them out as the only species in a 6 ft tank.
In that tank, I never saw the abhorrent behavior so commonly experienced by other aquarists that tried to keep them as single individuals, or just in pairs.
They often foraged together, sifting sand along the length of the tank in loose groups, without overt aggression, and that to me, was very interesting behaviour, and made for a great display.
