Introducing New Goldfish to a Tank

Introducing new goldfish isn't as simple as dumping them in the tank.
i Goldfish image by Lucy Cherniak from

Introducing new goldfish into your established tank isn't as simple as putting the new fish in. That not only could stress your new fish into death, it also could stress out the fish already there or spread disease to them.

Creating a Quarantine Tank

Quarantining is one of the safest methods of introducing new fish into your existing tank. However, this method is time-consuming, it requires you to plan in advance, and it takes patience and diligence.

To quarantine your new fish, set up a quarantine tank. A 10-gallon tank is usually sufficient for smaller goldfish; use a 20- or 50-gallon tank for larger goldfish. Keep an air-driven sponge filter in a healthy, already-populated goldfish tank. Fill your quarantine tank with water from the existing tank and move the established, cultured air-sponge filter into the new tank to cycle the quarantine tank. This helps establish the correct bacteria and various nutrient levels in the quarantine tank.

Acclimating Your New Goldfish

After the quarantine tank has fully cycled, your new goldfish need to acclimate to their new water conditions. Place your new goldfish with their shipping water into a clean bucket. Add tank water to the bucket every 5 minutes for one hour. Then pick up the new goldfish with wet hands and place them in the quarantine tank before discarding the shipping water. Monitor your new goldfish in the quarantine tank for several days before adding them to the existing tank, looking for parasites and any sign of disease.

Keeping It Simple

A quarantine tank isn't always necessary, although it's highly recommended. For those who have bought goldfish from box stores, disregard the common rule of "floating the shipping bag in the existing tank and dumping the fish in" to allow the temperature to become the same. Although this would bring the shipping water to the temperature of the tank, there are certainly a few more steps required. Instead of this, add a small amount of a detoxifying agent to the shipping bag, followed by 1 cup of water from the existing tank to the shipping bag, to help bring the temperature to that of the tank. Remove your new goldfish with wet hands and place them into the existing tank.

Tips For Healthy Goldfish

Peaceful cohabitation between your new and existing goldfish is the key to a healthy tank. If your existing tank is rather bare, consider adding more aquarium plants -- either live or plastic -- for additional hiding spots for your entire goldfish community. Also, remember that healthy goldfish sometimes grow to a length of 10 inches or more, so don't add too many fish to a too-small aquarium. Allow every fish in your tank enough space to grow and swim without obstacles.

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