They should eventually stop but if they get to agressive you can cup them and rearange and re release. The usual ratio is like... 4 or 5 for a ten gallon. You can also add a couple more girls. They usually fight less with more gals and your tank is big enough to get a few more. If you get a few more girls recup the others and rearrange the tank and release them that way. They fight because they try and establish a pecking order. You will almost always have a few nips out of the tails here and there though. Is there one picking worse than the others?