Ive has six tetras together for a good while now and for whatever reason I never thought the one tetra to be different. I have 5 glofish and the one I just realized is a different species is the black skirt tetra. I just now started reading about them online and they can be semi aggressive and a good chance they won’t school with different tetras. I guess I never realized because he/she has always schooled with the glofish. There are times the black skirt will go off on its own for awhile but it will stay with the group a good chunk of the time. Anyone have experience? I just thought it was pretty cool that mine isn’t aggressive seeming and does school. The black skirt is a decent size but the glofish are also pretty big. Every now and then the black skirt may “speed” at the other tetras but it stops instantly and sits with them.