20 to 40 gallon tank

[jackandrocco]

So I have a 20 gallon salt water tanks with sand and rock and everything and it’s been established for about 8-9 months and rn just has a damsel. And I have a 40 gallon tank rn with just 20 pounds of the same exact Agra-alive sand and just about 2 inches of rodi water to not have the sand dry out until I set the tank up.
Would I be able to dump the water rock and sand from the 20 gallon into the 40 gallon and then top it off with salt water to make a faster/close to instant cycle? If not is there a better way to do it?

 

[Gumbies R Us]

If you use some of the rock from the 20g, it would cycle the tank. Generally, I am a fan of using new sand in new tanks, but that is up to you!