
The barbs and the con will hold their ground. however, other fish with an old con, not so good lol
They chase them around!
I would Remove the Shark, add the barbs, then about 5-10 mins later add the shark again. Wait 1-2 weeks and then add the con. They should be used to eachother, Then when you add the con, there wont be so much agression since they are all to themselves. i hope this makes sense lol
Make sure you have lots of plants and rocks for cover, that will reduce the ammount of agression (if they are) between them, and will allow them to start over and have little territories