K9 has a whole list of options of what you can block, if you so desire you can select the "Block pornography only" option. They are pretty good in general.
You can have the filter gabbai do the password, and if for some reason you need access to a website which is blocked - contact him and he can check it out and unlock it for you.
(I can't find a direct link to the gabbai, I guess just pm guard or one of the administrators).