I would tell the pacus that water changes are only half the water. It ALL isn't going away,and it will be back soon, so there is no need to freak out EVERY time.
I would tell the pim that he can't eat his tankmates. Just because they are smaller, doesn't mean they are food. I would also tell him and the pacus to stop eating all the plants. I throw vegies in there for a reason.
I would tell the GT to stop picking on the gars. Some day they will be able to bite you in half, so stay on their good side.
I would tell the jag and oscar to stay friends. When they get bigger, they will rule everything together.
I would tell them that they are all my kids and that I like them more than most people.