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New-tank syndrome — ammonia / nitrite toxicity in ornamental aquarium fish

exotic_tox_fish_newtank

exotic-pet-toxicology en 2026-07-29

New-tank syndrome — ammonia / nitrite toxicity in ornamental aquarium fish

Source: Merck Veterinary Manual (merckvetmanual.com), a copyrighted veterinary reference. Per COPYRIGHT_POLICY §3, the points below are paraphrased derived fact summaries: numerical values and proper nouns are preserved from the source, but sentences are rewritten and not quoted verbatim.

Claims

  • *[Paraphrased derived summary — non-Open-Access source.]* Antimicrobial therapy is recommended if fish are dying.
  • *[Paraphrased derived summary — non-Open-Access source.]* When antimicrobials are warranted, base drug selection on sensitivity testing where possible.
  • *[Paraphrased derived summary — non-Open-Access source.]* Freshwater fish tissues are hyperosmotic to the water, whereas saltwater fish are hypoosmotic.
  • *[Paraphrased derived summary — non-Open-Access source.]* Key case details: number and species affected, duration, system volume and design, stock numbers and sizes, new arrivals, quarantine, and prior medications.
  • *[Paraphrased derived summary — non-Open-Access source.]* Prophylactic medication without diagnostic testing is strongly discouraged; it can drive resistant infections and other complications.
  • *[Paraphrased derived summary — non-Open-Access source.]* Toxicity often arises when total ammonia nitrogen or nitrite (or both) reach high enough levels.
  • *[Paraphrased derived summary — non-Open-Access source.]* Treatment includes reduced feeding, water changes, added chloride for nitrite toxicity, and checking that biofiltration is adequate.
  • *[Paraphrased derived summary — non-Open-Access source.]* Fishless cycling sets up the tank empty and adds ammonia to at least 1–5 mg/L.
  • *[Paraphrased derived summary — non-Open-Access source.]* Monitor the cycling process by regularly testing ammonia, nitrite, and nitrate.
  • *[Paraphrased derived summary — non-Open-Access source.]* Add fish only once ammonia and nitrite are no longer detectable.

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License & attribution

Source: Merck Veterinary Manual (merckvetmanual.com) is a copyrighted veterinary reference and is not openly licensed. Per COPYRIGHT_POLICY §3, every claim above is a paraphrased derived fact summary (numbers and proper nouns preserved, sentences rewritten), not a verbatim quotation.

  • https://www.merckvetmanual.com/

Sources

New-tank syndrome — ammonia / nitrite toxicity in ornamental aquarium fish
Source document: Merck Veterinary Manual / first-hand veterinary reference
Merck Veterinary Manual / first-hand veterinary referenceretrieved 2026-08-01

Verification file: pdf-raw/exotic-toxicology/fish.txt