GE clear silicone is the best, but like all silicone sealants it gives
off ammonia while it is curing. Be sure it is fully cured before it
contacts pond water. I have used it to hold coral together in salt
water tanks for years. I have never used the expandable foam (Great
Stuff) so I can't comment on it. My concern with foam is if it chips
off will the fish ingest it.
"Bonnie Espenshade" wrote in message
...
mark wrote:
hi can I use silicon to fill in the cracks in my waterfall,I want to
use
silicon so the water will not run down the cracks but flow over
them,should
I still use a liner. I'm a newbee to the waterfall so any advice on
water
flow is appreciated.



Yes, if it is pure silicone and has no ingredients to
inhibit growth of mildew. GE makes a clear silicone
which is great.

--
Bonnie
NJ
http://home.earthlink.net/~maebe43/