Aggressive Minnows

Hi, I added 8 White Cloud Mountain minnows to my Platy tank as I read they are schooling fish and get along nicely. However! They are constantly chasing each other and biting at fins, at first I thought they were just settling in but it’s been a few weeks they are still fighting, not schooling and they now chase my Platy fish too! (Who I am quite protective of!) there is one guy in there who is bigger than the rest and a different shade- he seems to be the main aggressor. Wondering now if he is even the same type of fish! What do you think and how can I resolve the situation before all my fish are super stressed!! In the photo the one on the right is the suspect in question next to the left which is a White Cloud Mountain minnow. Thanks!

What size is your tank they might be fighting for space

The fish on the left is a male and looks like a gold colour form of the white cloud mountain minnow. The fish on the right looks like a female of the normal colour form.

If you only have the 2 white clouds, get some more. That should fix the problem. try to have at least 6 (preferably 10) in the tank so they keep each other occupied.

Make sure you have lots of plants and if they do get annoying, the platy will be able to hide in the plants. But white clouds aren't normally aggressive so if it continues after you add some more, get rid of the mean one.