Mastering Freshwater Aquarium Ecosystems
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Fish Health (Cont.)

Malachite green, and formalin have also been effective against Chilodonella.

Skin Flukes (Gyrodactylus) and Gill Flukes (Dactylogyrus)

Skin flukes and gill flukes can live on aquarium fish at low enough levels that the fish do not display any symptoms of the parasite being present. Under poor water conditions or heavy population loads, skin flukes and gill flukes can reach very high numbers and cause severe distress or even mortality for fish. Typically, the symptoms that can be expressed are rubbing on rocks, wood, or substrate, rapid breathing, loss of appetite, weight loss, discolored gill lamellae and filaments, breathing through only one side (gill operculum [cover] clamped shut). Skin and fins may look cloudy or not as bright as normal. Fins on some fish may be clamped.

Both skin and gill flukes have a rostral hooked organ that attaches to the fish. The hooks puncture the skin or gills causing damage and irritation. The damaged tissue from skin and gill flukes can cause secondary infections and inhibit the ability of gills to extract oxygen from the water.

While both gill and skin flukes look similar under the microscope, there are differences. Skin flukes are live bearing and gill flukes are egg layers. Skin flukes have four eye spots near the non grasping end of the parasite. Because gill flukes are egg layers, multiple treatments are often necessary in order to eradicate the parasite. Medication often do not kill the eggs of gill flukes.

Discus and other cichlid breeders often have problems raising fry because of gill flukes in their breeding systems that attack newly hatched fry. Flukes can live on the parent fish and be passed to the fry. Adult fish often do not express any symptoms of infection, but can pass the flukes on to newly hatched fry. Because fry are so small, it does not take many flukes to cause mortality. Slow growth rate of juvenile fish can also be caused by flukes.

The preferred and safest treatment for flukes is praziquantel. Praziquantel is commonly available in the aquarium hobby as PraziPro. PraziPro is extremely safe and effective. The only side effect observed when treating with praziquantel was a temporary cessation of fish reproduction for about two months post treatment in livebearers.

Salt (sodium chloride, NaCl) is effective provided the fish you are treating can tolerate a specific gravity measured between 1.005 and 1.009 or 7 to 13 ppt. To achieve this level of salt you will need to add 1 to 2 tablespoons per gallon of water. Fish should be kept at this salt level for three weeks at 85°F (30°C). Once treatment is complete salt will need to be removed through water changes.

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