added 6 fish recently to my already 6 fish colony. got em for free. but it seems they are being punked to the upper portions of the tank. is there a good way to give em some shells so they dont die? id be happy to remove the two large males for a day or something to at least give em some kind of territory. rearrange the shell bed? maybe add more? im open to suggestions (they own half of a 55g) so plenty of space.