Looking for Non-toxic stone sealant that won't hurt fish.

[AvlJohn]

I recently had a fountain constructed from sandstone to feed my small koi pond. Because of the porosity of the sandstone and because I am in an area where it freezes and thaws during the winter I thought it would be a good idea to seal the sandstone to keep water from permeating the stone thus protecting it.

Does anyone out there know of a non-toxic concrete/natural stone sealant which is safe for fish. Water going into the pond would be flowing over the stone that I would like to seal.

Thanks in advance for any recommendations.