I know (now) that I should have at least 5 black skirt Tetras for them to be "happy" and school-I have 3. My one blue and my one green skirt tetras (BTW- bought before I knew how they got that way) are schooling with them, but my pink is always off hiding by her/himself. Do they differentiate by color? Are they all just Tetras to each other? if so what about the pink one Ms. Strawberry is always by herself I feel bad for her. everyone else seems fine; although as they grow I may need to get another tank. I will NEVER listen to the help ay my FS again. Thanks for your help. From a reply i realized i should explain better I have: 1 pink skirt always off by her/his self 1 blue skirt 1 green skirt 3 black widow.