Change the substrate to sand as well, they are sand shifters in the wild and do well with a sandy bottom tank.
They also should be fed a very varied diet but more on the vegetarian side, sex it is impossible to tell without venting the fish as they are monomorphic which means males and females look the same. Males are generally larger but that is not going to work with just a single fish
I would also not feed live feeder fish too much as it can lead to health problems, perhaps once a week with a week off in between.
I would really not add anything to the tank in terms of tankmates as "FRED" will see them as food unless they are around his / her size and of equal temperament which is aggressive!.
A nice piece of driftwood or fake plant cover would also be required, live plants they are like mini lawnmowers with and will clear them up almost overnight.
Very nice looking fish though.