How about adding something like this to the standard disclaimer presented when a user signs up for a login:
"At PNWMAS, we value our community and strive to maintain a "family-like" atmosphere. Like all families, we sometimes disagree and even argue. At other times, we may get a little goofy and kid around a bit (okay, a lot ) -- however, our main reason for being here is education and discussion related to the marine aquarium hobby. We may stray, but we always come back around. If this doesn't sound like the community for you, that's fine... there are many other hobby-related boards with very strict posting guidelines that you might enjoy. If this does sound like a place you'd like to spend some time, WELCOME!"