On 18 Aug 2003 13:06:44 -0700, (Todd) opined:

Here some good examples of Tufa Rock used in various Gardening Designs
with Bonsai and Alpine plants.

http://www.inlandtufa.com/tufagallery.htm

The tufa in the aquarium isn't toxic to the fish? I bought my husband a 150
gallon aquarium for his birthday and we're decorating it now. We want it to be
as natural as possible. We'd been looking for stones, slate actually, so we
could make ledges and levels for fish to hide and be happy as possible. We
intend on using as many fish as possible in this tank size...we'd like them to
be schooling and we'd like them to be neon tetras.

Now, back to the original question. What has to be done to the tufa to make it
ready for a tank? Won't it leach out too much base making the water very hard?