Okay! I just made a longish reply about the shell then realized that Ken already changed the shell to a rock so no more debate there, I think that is a safer and in fact more aethetically nearer to a real bog as I doubt if you can see shells like these in bog ponds.
David, I am not too sure if Ken meant it that way or not. But for me I hope what he meant was this:
"One more thing just to tell people that are making stuff like this .....Do not put shells in it....Which i already replaced with another rock..."
I think he meant making stuff like a Bog or a Mini Bog garden.... so he did not mean that members are making stuff up like calcium carbonate, etc.
I also am not too sure if it is a big thing or not (the calcium carbonate thing), but as mentioned above I think it really doesn't give a bog look if there is a shell anyway
I realized I just butted in on something that I am not too personally involved in, so I'll shut up now and hope Ken can confirm/clarify what he meant about the sentence.
TTFN
Arvin