Can you use one of those clam shaped sand pits as a permanent garden pond for fish or would the material harm the fish?
http://cgi.ebay.com.au/Aquaspirit-Shell-Pool/Sandpit-_W0QQitemZ370462404385QQcmdZViewItem?rvr_id=203362301438&query={query}&fitem=370462404385&linkin_id=8054961&mt_id=641&kw={query}
http://cgi.ebay.com.au/Aquaspirit-Shell-Pool/Sandpit-_W0QQitemZ370462404385QQcmdZViewItem?rvr_id=203362301438&query={query}&fitem=370462404385&linkin_id=8054961&mt_id=641&kw={query}