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SESK: Stuff Everyone Should Know · sesk.info/fish-no-bag-water

When adding new fish from the store bag, what should you do with the bag water?

Keep it out of your aquarium. It may carry germs.

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  1. Pour it in after the temperatures match
  2. Keep it out of your aquarium ✔
  3. Mix half of it into the tank

Why: Merck says never let water from the transport bag get into the aquarium. CDC adds that bag water may contain germs.

Huh, didn't know that: Merck suggests feeding the fish already in the tank as the new fish are released, to distract bullies.

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References

Answer: Keep it out of your aquarium. Merck says never let water from the transport bag get into the aquarium. CDC adds that bag water may contain germs.

  1. Merck Veterinary Manual: Providing a Home for Fish www.merckvetmanual.com/all-other-pets/fish/providing-a-home-for-fish
    When adding fish, never allow water from the transport bag to be introduced into the aquarium.
    Checked 2026-10-11.
  2. CDC Healthy Pets: Fish www.cdc.gov/healthy-pets/about/fish.html
    Try not to pour too much water from the bag into your aquarium at home because of the possible germs it may contain.
    Checked 2026-10-11.
  3. Merck Veterinary Manual: Providing a Home for Fish www.merckvetmanual.com/all-other-pets/fish/providing-a-home-for-fish
    feed the fish in the tank at the same time the new fish are released.
    Checked 2026-10-11.

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