How can I fix a fish tank leak?

Oh, dude, fixing a fish tank leak is like trying to stop a leaky faucet - you gotta find the source of the problem first. Grab some aquarium sealant, drain the tank (careful with the fish, they don't like moving day), dry the area, apply the sealant, and let it cure. Voila, leak fixed! Just don't expect a thank you from the fish, they're pretty ungrateful.