How long have they been in the tank? They look a bit stressed. The top is definitely a male Balzani, Gymno a South Amercian fish. It does require a temporary cool down period. The others could be a number of Geo's, not Tapajo tho. Could be brasilienses, surinamensis, altifrons, abalios , etc. As they grow and color up and their heads take structure you'll be able to notice. You have some large substrate. They are sand sifters as are the gymnos, your Balzani. They like to sift the sand for food that is their primary eating habits. If you have large substrate you leave them susceptible to injuring their gills as they sift the sand through their gills. If you intend on keeping the fish I would consider going with pool sand for substrate and possibly reading on the Balzani and it's cool down period. Good Luck! The Geo and Gymno species are a great fish and aoffer tons of color and personality to any tank.
