platy male

Hi, I have 4 platys, two male and 2 female (complete accident, just bought 4 and didn't realise the sex) the larger of the males has been nipping at the smaller younger male and causing quite a bit of damage, I know this is probably due to wanting to mate but Im just looking for a bit of advice...

Not sure if this is an emergency yet, but would appreciate someone else's opinion before I head off to work at 12.30! Yesterday I got a male plakat betta in my newly cycled 30L tank. No problem there - he seems to be settling in slowly.   About ½hr ago I noticed in the 60L tank that there was a...