Ichthyophthirius multifiliis Infection of Botia macracantha Larvae and Acute Toxicity Trails Using Sodium Chloride and Formalin on Larval Fish
IAAAM Archive
Eric W. Curtis; Roy P.E. Yanong; Craig A. Watson; J. Scott Graves
Tropical Aquaculture Laboratory, Department of Fisheries and Aquatic Sciences, University of Florida, Ruskin, FL


Ichthyophthirius multifiliis ("ich"), a holotrichous ciliate, is a common and significant problem to aquarists and commercial fish producers through out the world.2 AS a parasite that appears to infect most freshwater fishes, ich has been widely studied.5 There have been numerous studies focusing on the acquired protective immunity of fish surviving an ich challenge.1 An ich infestation can cause massive mortalities if left untreated. 2 There are several available methods for treatment and control of this parasite, some of which are: formalin, a formalin malachite green mixture, elevated salt levels, increased water temperature (>30°C) for 10 days, copper sulfate, potassium permanganate, and UV filtration.2,4

Botia macracantha (clown loach), from the family Cobitidae, is a commercially important tropical fish within the aquarium hobby trade. Almost exclusively wild caught, loaches are collected from rivers in Indonesia and shipped around the world. Difficulty spawning and poor survival and growth of young have led to limited success regarding the culture of this species.6 Having small inconspicuous scales the species is particularly prone to infection with ich.5 We documented the treatment of an ich infection of newly hatched loach larvae.

Feeding stages of ich, called trophonts, can be seen on Day 1 larvae, around 24 hours post-hatch. A few larvae were brought into and held in the laboratory before the remaining larvae went through a series of treatments. 48 hours post-hatch, the outside tank was treated with 12.5ppm formalin and 1.1-1.2 ppt salt. A 70-80% water change was done about 4 hours later. Salt was added to maintain a concentration around 1.1-1.2 ppt. We began to see dead larvae soon after treatments. On Day 4, after a water change, the larvae were once again treated with the same concentration of formalin and salt. Approximately 4 hours later a final water change was performed followed by addition of salt to maintain a 1.1-1.2 ppt concentration. There were no surviving larvae from outside to observe the following morning. The larvae that were brought into the laboratory survived until the infecting ich organisms had exited the larval bodies (Day 6) at which point the larvae were preserved for histological studies.

Ich has been documented to infect newly hatched tropical fish larvae. An earlier study hesitatingly stated that newly hatched blue gill larvae were resistant to ich infection for about one month with the reservation that further studies needed to be performed.3 Few studies have been published on tolerances of newly hatched tropical fish larvae to various chemical treatments for ich. Tolerances at 1.5 and 3 ppt salinty and 12.5 and 25 ppm formalin were examined on newly hatched larval characins and cyprinids instead of newly hatched loach larvae because of the availability of the former two.


1.  Dickerson, H.W. and T.G. Clark. 1996. Immune Response of Fishes to Ciliates. Annual Review of Fish Diseases 6:107-120.

2.  Francis-Floyd, R. and P. Reed. 1991. Circular 920, Ichthyophthirius multifiliis (White Spot) Infections in Fish. Gainesville, FL, Florida Cooperative Extension Service (FCES), Institute of Food and Agricultural Sciences (IFAS), University of Florida (UF).

3.  Hoffman, G.L. 1999. Parasites of North American freshwater fishes. Comell University Press, Ithaca. p. 41.

4.  Noga, E.J. 1996. Fish Disease: diagnosis and treatment. Mosby-Year Book, Inc., St. Louis.

5.  Stoskopf, M.K. 1993. Fish Medicine. W.B. Saunders Company, Philadelphia.

6.  Watson, C.A. 1991. Fish Under the Volcanoes" Part I: Clown Loaches. Freshwater and Marine Aquarium 14" 40-44.

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Eric W. Curtis

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