Aggresive Black Ruby Barbs

[Dana C]

I have had 5 Black Ruby Barbs for about 2 months with no problem but this morning I noticed my Bronze Cories have all got little nibbles out of their top fins.
I saw the barbs keep going down to them and the cories swimming off madly sometimes the barbs follow and sometimes just swim the other way.
I have just seen 4 barbs chasing 1 cory and they seemed to trap him in a corner.

Is this a common problem because I checked before I bought them and every where said they are peaceful.
Is there any thing I can do to stop this?
I am going to add more plants so there are more hiding places will this help at all?
I think the cories may have been breeding in the past few days even though I haven't seen any eggs would this have any thing to do with it?

Thanks for any replys.

 

[Dana C]

Sorry to post again but I didn't get any replys.
Do you have to have more females than males for black ruby barbs or doesn't it matter?
I just thought if there was more males maybe this is why they are getting aggressive.

As you can tell I am trying to come up with anything to stop them biting my cories.
If I was to take the barbs out and put them in there own tank what size would it have to be?
I have a spare 25 litre tank would this be ok or is it to small?

Any advice would be welcome