"A.N.Other" wrote in message
...


I don't think that the leaves themselves are poisonous; it would depend on
the type of tree.

There may be a couple of problems created as the leaves rot

1) The process of decomposition may consume the oxygen in the water
and
the fish suffocate.

2) The decomposing material may produce toxins, one I can think of is
Hydrogen Sulphide which very toxic.


The trees are walnut trees.