You can’t bring your goldfish back to life if it’s already dead. However, if your fish is dying but still showing some signs of life, there are some measures you can take to revive it.
First, separate the goldfish from other tank inhabitants. Place the dying goldfish in a container filled with cool water from its tank. Place an air bubbler or air stone in the container to provide extra oxygen for the fish. Then, hold it gently and check its body for injuries. Be sure to remove any debris or dirt from its body.
Use your fingers to gently open its gills while making sure the fish stays submerged in the container. Give its underbelly a gentle massage to stimulate breathing, then move the goldfish closer to the air bubbler or air stone.
Keep your fish in the container for at least two hours before moving it back to its regular tank. Feed it veggies and low protein foods for a couple of days while it recovers.