Best way to seal crack in hard shell liner
We have a kidney shaped hard shell liner it is pretty small but had developed a stress crack where the shell kind of buckled underneath. We sealed up some side holes years ago where previous owners put wires through the sides I guess. We used Marine Caulk and the rubber from an old popped ball. Now I don't know how to tackle this new crack as I know the Marine caulk is probably not good for the fish and we don't have a rubber ball to seal it up like we did last time. DH seems to think we can heat up the liner with a heat gun but that doesn't seem long term to me. Anyone have any other suggestions.