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VETCARE Ô |
CHEMICALS |
AQUAHEALTH Ô |
FORMALIN
Formaldehyde sol. 37% vol.
EXTERNALLY APPLIED
ANTI-MICROBIAL & ANTI-PARASITIC AGENT
Description:
Formalin is a colourless transparent liquid with characteristic sharp odour
and specific gravity 1.09kg/lt. (20°C).
It is a virtually
saturated solution of formaldehyde in water. At normal water temperatures it
contains 34-38% w/w formaldehyde. For aquacultural purposes it is usually
supplied containing 12% methanol to slow down the polymerisation of the
formaldehyde.
Indications:
Formalin is a widely used anti-parasitic agent, effective against many
protozoans and monogenetic fluke parasites of fish skin and gills. It is also
active against many bacteria, such as the Gram negative filamentous bacteria
infecting the fish gills. Formalin is safe even for small fish when used in
baths according to proper protocols.
Apart from its therapeutic use, formalin is used also for prophylaxis
against the ecto-parasites in order to prevent the seasonal build up of
parasitic loads on caged fish, or the proliferation of the parasites on
valuable brood fish in hatcheries.
Formalin dilutions may be used as a
strong disinfectant in hatcheries.
Administration:
It is recommended that a light dilution of formalin (1:100) is prepared
and gradually dispersed in the fish tank or tarpaulin until the required bath
concentration is achieved.
Diluted Ο2 should remain at the
safe levels of 6 to 8ppm. Formalin baths should last up to 60 minutes and
may be repeated according to veterinary instructions, depending on the season
and the type of parasitic infestation under treatment. Formalin baths are not
recommended when the water temperature exceeds 26°C.
Diluted solutions are normally designated by their content of formalin,
not of formaldehyde; for example a use concentration obtained by diluting
formalin 1:10,000 will be designated 0.01% formalin or 100ppm formalin but
actually contains about 37μg/ml (ppm) formaldehyde.
The maximum safe formalin concentrations in baths differ according to
the age/size of the fish and the level of dissolved oxygen in the water.
Formalin is a reducing agent, which will absorb oxygen from water; in addition
it irritates the gills and lowers the efficiency of osmoregulation and gaseous exchange at the
gill epithelium. Besides, when formalin baths are applied, the bacteria and/or
the parasites, which the baths are meant to destroy, have already impaired the
gill function. Therefore, water aeration, or preferably water oxygenation,
should be provided throughout a formalin bath.
Indicative
formalin concentrations for hourly baths (sea bream and sea bass):
·
Fry 0.3g-0.5g: 30ppm · Fry 0.5g-1.5g: 50ppm · Fingerlings 1.5g-3g: 80ppm
· Fingerlings 3g-20g: 120ppm · Caged fish >20g: 150ppm · Brood-stock: 200ppm.
Precautions
(for operator safety):
Formalin is toxic and caustic for
the skin and eyes as well as for the upper respiratory tract when fumes are
inhaled and the gastrointestinal tract if accidentally swallowed. In the eyes
formalin is very irritant, even in considerable dilution. Always flush exposed
eyes or skin with plenty clean water for several minutes. If accidentally
swallowed, the patient should drink plenty of water, vomiting should be induced
and demulcents taken. Subsequent to such first aid measures proper medical
advice should be sought after.
When handling
formalin apply safety measures and use proper equipment. Keep away from children.
Packaging
and storage:
Formalin is distributed in sealed
plastic containers of 27kg (24.8 lt.), most often 30kg (27.5 lt.) and up to
35kg (32.1 lt.).
It should be stored in a ventilated, dark place, away from oxidising
agents. Storage temperature should exceed 10°C. (Polymerisation of
formaldehyde to the toxic polymer, paraldehyde, occurs faster in sunlight and
at low temperatures.)
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Copyright (c) Dr Panos Varvarigos