I have just two remaining male guppies out of 10, I call them blondie and ginge and they do not get on very well. Since the others got poorly and started dying blondie has become bigger and more aggressive. I had assumed he was a short tail but even his tail has fanned out and become much larger than his conpanions from the same batch. Every time one got weak he has bullied them relentlessly and now ginge hides all the time. What is the best way to reduce aggression in guppies?