I have one that who will trim his tail because it's so big, and another that bites sometimes out of boredom. Giving him more decorations in his tank seemed to help a lot, so I've got extra things and I'll trade out different things whenever I do a 100% water change. So I might take out his hamster tunnel and put in a ship decoration one week, and take the ship out and put in an arch the next week.
I use AQ salt when the biting looks bad, but I've never used any other kind of medication. Once the biting stops, it doesn't take too long for the tail to grow back.