There's no rule like that, just location and picture.
I think the OP is referring to this, and he/she didn't realize the 50 posts is only for NON AQUARIA related items for sale. viewtopic.php?f=12&t=4998To sell Non-Aquaria related items, you must have 50 posts in the forums before you can create "Sell threads" in the Buy, Sell, Trade forum. Posts such as (cool, very cool, ditto, sweet, etc) do not apply towards a 50 post count. Our mission is the exchange of hobby information, not commerce, and the Buy, Sell, Trade forum is a perk for those members who support the mission of the Wisconsin Reef Society.