I've been sitting here watching one (allegedly) female cherry barb chasing and nuzzling (for lack of a better word) another female cherry barb, and it's been going on for a while. It's the behaviour I would expect of a male, but both of these look like females. I have three males and four (allegedly) females in this tank, and they're all mature enough for it to be obvious, supposedly. Could it be a 'sleeper' male? Is it a dominance thing amongst the girls? Is it play? The 'chasee' could swim away, but she's not trying that hard to get away from the other one.