About a month ago i upgraded my tank from a 80 litre to a 125 litre. During the last couple of weeks my Male BN is being quite nasty to the other fish when they go near him chasing them out of the way. I also have a definate Female BN and he chases her too. He has plenty of hidey spots and wasnt like this in the smaller tank why is he doing it now? , i have recently lost a cory too and was wondering if he could of killed it? Any advice gratefully received. Other fish in the tank are guppies, mollies, platies, corys and apple snails.