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Chloroquine phosphate
Common Name(s): Chloroquine
Molecular Formula: C18H26ClN3
Used For: Treatment of Cryptocaryon
Caution: Avoid exposure
Material Safety Data Sheet: Chloroquine diphosphate


Chloroquine phosphate is a drug used within the marine aquaria hobby for the treatment of Cryptocaryon. It is actually used in the treatment and prevention of malaria. Commercial brands include Chloroquine FNA, Resochin and Dawaquin. It is an anti-protozoal drug, killing the therots stage of Cryptocaryon on excystment from the tomont, thus stopping re-infection of new fish. Non-toxic to most fish at correct dosage rates (5-10mg/lt) but highly toxic to algae and some invertebrates. Non-toxic also to bacteria. Needs to be purchased through a qualified medical practitioner (either a medical doctor or veterinarian).[1]

Chloroquine phosphate is a proven treatment for Marine Ich and Marine Velvet[2]. It is not toxic to fish at therapeutic levels. See also Quinine.



Dosage rate is 5 to 10 milligrams per litre[1][2], every 5 days for at least 4 treatments. Works best in conjunction with hyposalinity (under 14ppt) [2].

Conversions between quinine forms, 100 milligrams of quinine is equal to[3]:

  • 111 mg quinine hydrochloride
  • 169 mg quinine bisulfate
  • 122 mg quinine dihydrochloride
  • 121 mg quinine sulfate
  • 160 mg quinine gluconate

Note: light should be turned off during treatment.

Amyloodinium ocellatum

10 mg/L for 21 days. Observe fish after treatment in case another dose is required.[2]



  1. 1.0 1.1 ( Porritt, M., Cryptocaryon irritans, Reef Culture Magazine, 1.
  2. 2.0 2.1 2.2 2.3 (Noga 2010): Noga, E.J., Fish Disease: Diagnosis and Treatment, 2nd ed., John Wiley & Sons, 2010.
  3. wikipedia:Quinine