Thanks guys for the informative answers. Seems I can, and should, use the
limestone chippings and worn pebbles.

My only problem now is that the crushed chippings contain some very small
sharp flakes which may harm the lining. I don't seem to be able to sieve
these out since I cannot get the chippings dry enough - even a small amount
of moisture makes the very small flakes stick to the larger pieces. Washing
is not reliable for much the same reason.

many thanks, Davy

"Davy" wrote in message
...
I intend to put stones or pebbles in my wildlife pond which won't have any
fish apart from maybe the odd stickleback. My preferred pebbles are
limestone but I have seen a warning against using limestone pebbles
because
they can change the ph. Should I take this warning seriously?
thanks, Davy