Carbon should not be use unless u build up new or rebuild that tank. That is also optional cause normally it mean more for rebuild since you need to let the fish back to tank back to asap.

for new tank just put in a dirty sponge (can ask from lbs foc) to kick start the cycle in a fishless tank after 1-2 days fillup.

You can just kept it. Will be useful once you need rebuild the tank. As for med, i never use med for pass 3 years.