SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/fish-test-new-tank

Which water tests matter most during a new tank cycle?

Ammonia and nitrite, because both are toxic.

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  1. Ammonia and nitrite ✔
  2. Only temperature
  3. Only pH

Why: Ammonia and nitrite reveal whether cycling bacteria are established. Nitrate is useful to watch later.

Huh, didn't know that: Merck advises testing ammonia and nitrite daily until the filter is cycled.

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References

Answer: Ammonia and nitrite. Ammonia and nitrite reveal whether cycling bacteria are established. Nitrate is useful to watch later.

  1. Merck Veterinary Manual: Environmental Diseases of Aquatic Animals in Aquatic Systems www.merckvetmanual.com/exotic-and-laboratory-animals/aquatic-systems/environmental-diseases-of-aquatic-animals-in-aquatic-systems
    Daily monitoring of TAN and NO 2 coupled with frequent water changes ... will be necessary until the biofilter cycles.
    Checked 2026-10-11.

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