Costia Chilodinella parasites of gold fish and koi
The descriptions of the common fish diseases have been deliberately kept simple to assist the understanding of the basic problems that may be encountered. This is a fascinating aspect of pond keeping and massive amounts of resource for further study can be found across the Internet.
The key to disease control is observing gold fish or koi behavior. Any lasting changes to normal behavior should be investigated because this is the first indication that something in the pond might be wrong.
A correct diagnosis normally needs more in-depth examination often using a microscope.
Costia & Chilodinella
These are parasites of freshwater fish that can be responsible for mass destruction of goldfish in a small amount of time. Salt again is the solution. Costia can attach themselves or swim freely. When attached they look like small "commas" stuck to the gill or skin. If a lot of goldfish are dying then be suspicious of this disease.
Chilodinella is a heart shaped organism, or a large round organism full of tiny bubbles. Chilodinella succumb easily to salt treatment at 0.3%. 14 days treatment is recommended and make sure air is used profusely to compensate for gill damage. If goldfish are dying on the surface in large numbers then suspect Chilodinella.
Dr Erik Johnson of koivet.com has provided the following salt treatment schedule to remove Ich ...
Remove valued live plants.
2. Raise temperature to 80 degrees F (26 degrees C max), tops.
3. Increase aeration! ... always important in any stress situation
4. Add one teaspoon of salt per US gallon.
5. Twelve hours later, add another one teaspoon of salt per US gallon.
6. Twelve hours later, add another one teaspoon of salt per US gallon.
7. Within 48-60 hours of the second salt dose at 80 degrees, the Ich will be gone.
8. Leave salt in the water for another 3-5 days unless you're worried about your live plants.
9. Remove salt via partial water changes. (30-40% at a time if desired).
To convert to Imperial gallons the factor is 1 Imperial gallon is 1.2 US gallons
Please also check out this UK Pond Doctor site
What to do if you suspect disease problems
Test for Ammonia, Nitrite, and pH at a minimum, and preferably also test for Total Alkalinity and possibly Hardness.
Ammonias are lethal in their own right and worse at higher pH. If dead fish exist this will also create ammonia problem. pH can change overnight if the system loses its buffering capacity (this would show on a test of Total Alkalinity)
Aquarium Pharmaceuticals basic drop type test kits are most accurate according to experts. Review USA on-line pond supplies
In the case of Ammonia accumulation:
If water quality is suspect begin a systematic daily changing of 20-40% of the total volume in the system. But beware of major temperature changes the system. A small addition of salt at .1% level will do no harm.
Interesting articles on Gold Fish & Koi
Fish Health Bacterial Ulcer Disease Aeromonas and Pseudomonas
Fish health Dropsy or Pine Cone Disease
Gill Flukes Skin Flukes of gold fish and koi
How to Recognize and Treat basic Fish Health & Disease Problems
Ich parasites of gold fish and koi
Koi Disease Gold Fish Diseases In Garden Ponds White Spot Ulcers