|I have built a new pond using rubber roofing material as a liner. Is this safe for fish?
Sixty percent of what you'll find in rubber roofing material is safe for fish. Forty percent of the time, the fish will be flashing, scratching and dying within 14 days. It has everything to do with the fungicidal powders and elastomizers (things that keep rubber 'stretchy') that they put into the rubber roofing material.
Rubber liner for ponds was "born" on the roof. Later, companies just started modifying the formulas to come up with fish safe products.
It's a crap shoot, when you try using roofing material for ponds, and considering that rubber liner is available at or below manufacturers cost (less than forty cents a foot) from various online places, why risk it.