Fish Pond Construction Problem.

[adjer]

How can I protect my fish from toxic alkaline levels from the mortar mix after I have built the stone surrounds & waterfall? ie rain water from the mortar joints will run off into the pond water. I understand that vinegar or baking powder can be used as a neutralising agent. How is this used? Is it added to the mortar mix & in what proportions?
Another method is to paint the joints with something but I don't know the name of the product. All ideas welcome.
Thanks Adjer.

[judekn]

Hi if you go to a garden centre that sells fish/ponds etc, they will be able to advise, there is a product that is painted on and seals the mortar etc, but cannot remember its name,