u/alyciamrs68

I added a black skirt tetra to my tank of glofish tetras. Pet store worker said that this would be fine as they are basically the same fish. However, in the last few months since I introduced it to the tank, my two oldest Glofish have died. My water parameters and temperature are good and I do regular water changes. Could it be because of the black skirt tetra? I do see it chasing my other glofish and they tend to hide from it a lot. Any ideas? Thanks!