If I've got a giant snail shell , a sand dollar,an osyter shell (only one), and a conch shell . Should I bother to add any crushed coral (if so how much, I've got 2 lbs).
What're you trying to do with it? Just for looks or the have more alkalinity buffer? Those shells will make a difference but not much of one. It depends on the size of the tank. Most salt mixes usually are pretty good buffers in themselves.