Summary: Various fish parasites, some normally free-swimming organisms, and various species of algae can become a problem. What to consider, and some examples of treatment.
Publication: Staff Operational Handbook, J.L. Scott Marine Education Center & Aquarium, Biloxi. MS.
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.
- 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.
1. Prior to display to help prevent introduction of disease/parasite problems to closed system display tanks.
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.