the oyster shell (assuming its the crushed type you pick up at the local
co-op) will separate and come to the top of the sand and it most of the time
has a dark (or gray) coloration to it so it is not as attractive as the
white crushed coral.

but its no harm using it.


kc

"RNP" wrote in message
...
I have just set up my latest marine tank using a crushed oyster shell and
sand mix............ Is this going to be ok ??

It's only a thin layer of course. My other tank uses coral grit but I
fancied a change......... Just wondered if anyone has any thoughts on this