55 with red head tapajos geophagus is probably a bit small. I guess you could put 1-3 in there, but they like to be in groups of 5+, especially as juveniles.
If you were to grow up a group in a 100+ and got a pair, you could put them in a 55, but I wouldn't start in a 55.
If you were to grow up a group in a 100+ and got a pair, you could put them in a 55, but I wouldn't start in a 55.