The secret is in the liquid polymer
Sounds like an acrylic and in that case it is not expected to be toxic after it cures. Its likely to take 24 hours for a complete cure and set. You will have to get all (100%) of the algae and bacteria out of the scratch to be effective or you will seal in a permanent line. Wipe excess off as industrial metals contamination in products like this can be higher than you want in a reef tank.