[Delphinus]

I find they really need to be fenced in. I think it's best if they go on the rockwork, there's some debate over this point, but without getting into it too much I still think it's better if they are on the rock ... but they need to be a bowl/depression in the rock so that they can't roll out of there (ie., they won't roll uphill). I usually end up epoxying rubble and small rocks around them. Once they're secure they usually end up attaching on their own. They won't attach if there is too much movement possible (ie., they still need to open and close obviously) but too much rocking motion from the the current is enough to prevent them from laying down those byssal glands and then they'll be constantly on the move.