This what you are doing...from Spruce Pets.
Seeding a
new aquarium has become a popular practice. It is the process of transferring nitrifying bacteria from an established aquarium to a new aquarium. Seeding gives the new aquarium a jump start on the cycling process. Normally, it takes 4-6 weeks for the growth of beneficial bacteria to complete the nitrogen cycle in a new aquarium. It is not unusual for seeded aquariums to fully
cycle in half the time it would normally take, thus allowing you to stock more fish in the new tank sooner. Seeding also helps to reduce stress on the fish and reduces or eliminates fish loss due to the startup cycle.