Parasites and Similar Problem Organisms
by Dr. Adrian Lawler
Extracted from the staff Operational Handbook which Dr. Lawler wrote as Aquarium
Supervisor for the J.L. Scott Marine Education Center and Aquarium, of Biloxi, MS
Aquarticles
As tanks in our aquarium are all closed systems, there is the potential that various
organisms introduced with the display animals can multiply greatly and cause problems in
the health of our animals. Problem organisms can be various fish parasites, normally
free-living organisms, and various species of algae.
In order to know how to treat a tank one must know what species one
is proposing to treat. The species must be identified as best as possible (using
appropriate texts). Then use our treatment "bible," Herwig (1979), to find a
suitable drug and method of treatment for the organism in question.
Treatment can be dependent on the following:
- Species involved
- Whether treatment takes place in display tank or back-up tank
- Volume of tank (some drugs may be too expensive)
- Value of display organisms (if easily replaced it may be simpler to chlorox the whole
tank and start all over)
- How dangerous the organism is (if one has parasitic dinoflagellates, the tank is small,
and the display organisms are common it is best to kill everything before the parasite
spreads).
All of the previous must be considered when proposing a treatment method; a parasite
may be treated by different methods depending on the situation.
There are two main times to treat fishes for the aquarium:
1. Prior to display to help prevent introduction of disease/parasite problems to
closed system display tanks.
2. After fish in a display tank show a disease/parasite problem
Treatment prior to display involves holding fish for one to seven days after capture so
they are less stressed and minor skin and fin damage can heal or major skin and fin damage
becomes more visible. Badly damaged fish are released or discarded; fish suitable for
display are treated with appropriate drugs (see Herwig, 1979) to rid them of monogenetic
trematodes, parasitic dinoflagellates, Cryptocaryon, etc. External copepods,
isopods, leeches, and Argulus may have to be removed by forceps after use of
MS-222 (Tricaine Methanesulfonate anesthetic). Treat fish in all-glass tanks with sponge
biological filters. After treatment is over stock out treated fish, discard
water in tank (with treatment chemical), and add clean water so the treatment tank is
ready to receive the next batch of fish.
Use MS-222 (add slowly) in a minimum amount of water of the proper salinity to put fish
to sleep in order to examine live fish for external or gill parasites or to remove such
parasites. Remove large external parasites with forceps; gill isopods have to be removed
by cutting legs off isopods (with small scissors) and then carefully pulling (with
forceps) legs out of gills to avoid gill damage. Make sure gills are working throughout
process (too long in MS-222 leads to death); return fish to clean water as soon as
possible for revival.
Fresh water dips for saltwater fish and saltwater dips for fresh water fish will
dislodge some external parasites. Length of dips will vary per species; usually three-five
minute dips will suffice, remove fish if they go into extreme distress.
Use diatom powder in a DE or canister filter to remove water-borne parasites from a
tank, or to speed up wound healing.
Unless the biological filter will not be affected by the treatment chemical, do not
treat fish in a display tank; a killed biological filter will lead to ammonia build-up and
another problem.
Do not overdose fish (with too much drug or too long in treated water). Sometimes it's
a fine line between killing the parasites and killing the host.
Reference: Herwig, Nelson. 1979. Handbook of Drugs and Chemicals Used in the
Treatment of Fish Diseases. Charles C. Thomas, Publisher, Springfield, Illinois, 272
p.
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