Following the completion of my tank cycle I picked up six male platies on the weekend. Two black and white, two red and white and two pale blue.
One of the pale blue turned out to be female so was relentlessly chased, as was the pale blue male, and I returned and swapped it for another pale blue male. I was hoping that once the female was out of the tank they'd leave the blue males alone but this was not the case. The main culprit was a red and white one, but all of the fish were chasing it and trying to have their way.
The following day I returned the two blues and swapped them for two solid red males. I'm 100% that there are no females in the tank. Now the two black and white fish are almost constantly harassing the two red ones. The two red and whites aren't interested. They are displaying mating behaviour again, doesn't look like the male vs male aggression I've seen when they have the odd peck at each other.
I'm at a loss.
Tank is 98cm long, 210 litres, cycled with ammonia, results a stable amm 0, nitrite 0, nitrate 10 and have been since I added the fish, I've been testing twice a day. It's a moderately planted tank - am waiting for plants to grow in.
Does anyone have any idea why they are behaving like this? I read that an all male group of platies is no problem - is this not the case?