Costia

Costia is another one of those parasites that you can't see without a microscope.  It will run down your fish's immunity system and open the door for other complications such as ulcers, fin rot and other bacterial infections.  It's similar in habit to Trichodina and Chilodonella but tends to be a little more stubborn and, I think, a little worse on the fish.  They all three are microscopic and are basically treated with the same medications as what kills ich.  Costia is not as common as the others and it's so tiny it's harder to find, even under a microscope's lens.

How to Recognize, Treat and Prevent Costia in Your Koi or Goldfish Pond

Most parasites that affect koi and goldfish cannot be seen with the naked eye. Under the microscope Costia looks very similar to the drawing above except the drawing doesn't allow you to see how very tiny they are.  You must have a sharp eye to see them dart across the lens view because they are as quick as they are tiny. Costia looks like tiny commas.  They move quickly in circles and on straight courses, often swimming vivaciously in fluids trapped by the slide cover.  Unless you have super-human eyesight you can't see Costia without placing a mucus scraping under a microscope. 

Recognizing Costia

These little rascals, like all koi and goldfish parasites, are active - tiny and extremely quick - and will tickle the fish as they dart around on the skin.  The fish will scratch themselves as best as they can, taking a "running" jump and scraping against the walls and floor of the pond to relieve the itch.  We call this "flashing". Other behavior the koi may exhibit is spastic swimming or spiraling, even jumping. 

The only sure-fire way of diagnosing Costia is to do a mucus scraping on the suspect fish.  Like I said - you better look close at that slide.  It's quite interesting and, if you can get your hands on a microscope, quite easy to do.  When looking under the microscope if you find anything that moves on its own chances are it is a parasite and, if it looks like tiny and fast moving commas, it is Costia. 

Treating Costia

It's not as easy to treat Costia as the other parasites because Costia has become immune to the affects of salt.  Many of the other parasites - Ich, Trichodina, and Chilodonella - can be treated with at .3 % (3 lbs. per 100 gallons).  Our tests have shown that salt at this volume will not kill Costia.  We have actually brought the salt up to twice as much dosage-wise and finally was able to kill them but we do not suggest you try a salt treatment at that level.  In other words - stick to the other ways to kill Costia.

We suggest you use either ProForm C or QuickCure.  If your water temperature is not very warm you should use the ProForm C.  You can use Quick Cure in spring or summer but not when the water is cold.  Quick Cure is part of our Parasite Pak that addresses flukes, fish lice and anchor worm as well as Costia and other parasites like them.

You may need to change most of or a portion of the water when treating for parasites.  Make sure to have de-chlorinator on hand.

Treatment has to be done on the whole pond because if one fish has a parasite, all of them do.

Emergency Procedures

1. Treat the whole pond with either ProForm C or QuickCure.

What to Expect Next

Once Costia is eradicated from your pond you should not have any residual affect from either the parasite or the treatment except maybe that the fish have been stressed so that they are susceptible to anything that may come along.  Just be "gentle" with the fish for a while and keep an eye out for ulcers or other problems that arise when fish are stressed.

Preventing Costia

Quarantining and treating any new koi or goldfish is the key to preventing any infestation of any parasite, including Costia. 

More Information About Costia

• Buyer Beware - The Importance of Quarantine
• Flash Dance - A Closer Look at Parasites

Items You Might Need:

Parasite Pak

ProForm C

Doc's De-Chlorinator

Know Your Gallons!

Heavy Duty Water Meter

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