WHY QUARANTINE YOUR GOLDFISH
Quarantining new fish means to keep them in an independent system, completely separated from the pond or tank. It is ALWAYS recommended to quarantine all new fish, no matter where the source comes from. It's not that his goldfish are sick, but the stress will weaken their ability to fight off any infections or outbreaks. You would be putting your other fish at risk if not separating them. It is recommended to quarantine for a minimum of 7 days before introducing the new fish to your primary pond or Aquarium. Please let the fish rest a few days before starting any treatment.
Today, goldfishes comes from many sources such as Thailand, China, Taiwan, and USA. If new goldfishes are introduced into the same fish tank which already has other goldfishes, sometimes the bacteria mixes and one or more of the goldfish may become sick as a result. Apart from that, when two independently healthy goldfish are mixed together, one may become sick in the process. Often times goldfish will have a resistance to the bacteria they carry in small amounts and it may not make them sick unless they become stressed. At such a scenario, they may be overcome with the bacteria they carry.
It is recommended that when carrying out quarantine to first of all have their own equipment, such as tank/tub, nets, sponge filter for a minimum time of 7 days to avoid cross contamination. You should clean the quarantine tank either first or last and ensure you wash your hands and arms between the process of cleaning the quarantine tank and your other existing tanks
QUARANTINE PROCESS FOR RECEIVING NEW GOLDFISH
Adequate space should be provided based on the goldfish's size. If you don't have an aquarium, you can use a plastic storage bin. You would fill it, and add an airstone for Aeration. Setting up the water prior to receiving is more beneficial and will give time for the water to age. Adding a heater to make the temp 75-80 F will help them adjust as well because they are from Thailand, the water is warm there year round.
When you first receive the fish they should be placed in a tank that has salt at concentration of 1–2 tablespoons /10 gallons or 0.30 PPT. This helps them deal with stress. Don't feed the goldfish when first putting them into the quarantine. Use some Methylene Blue to help with recover. Add a few drops in or simply follow the instructions on the bottle.