fast setting something

[rossb]

A bit ago I posted a question about a safe sealant that works underwater and will fill a gap of about 3/16th inch. As I expected it likely doesn't exist. The next best thing is something that cures quite quickly, 3-4 hours ...and then is fish safe. Does anyone know of something like that?

I have several sealants that are safe after 24 hours but I am not sure how long a person can leave their tank without the pumps running.

Any suggestions?