Another dead-koi puzzler in Fresno

-As in 2001, officials perplexed at Shinzen Garden.

By Cyndee Fontana / The Fresno Bee01/19/07 04:55:54

In late 2001, about 200 colorful koi fish died in a single bad day at the Shinzen Friendship Garden in Woodward Park.

Fresno city officials labeled it a catastrophe and spent thousands of dollars searching for the cause. Was it a virus? Contaminated water? Faulty pond filtration? A lightning strike?

The mystery was never solved. And today, almost exactly five years later, koi that replenished the pond after that calamity again are dying at an alarming rate.

Of the 50 or 60 fish once swimming around, by city estimates, only seven were left Thursday morning. The die-off that began around Christmas — before the bitter freeze — is another puzzle.



Comment:
This is a really sad story, to which there is not much more I can add as the water has been tested for poisons and more.

My only observations based on my pond keeping experience and research is two fold;
It is possible there were Ichthyophthirius multifilis tomites present in the water, and considering the severe cold wave that hit Fresno in the last week may have stressed the fish brought this infestation.

The other possibility was something stirring up the muck on the bottom of the pond (even a small earthquake!), causing the Hydrogen Sulfide in the muck (a by product of anaerobic bacterial decay and the Nitrogen Cycle) to be suddenly released.

More information about the Nitrogen Cycle:

NITROGEN CYCLE AND AQUARIUM CYCLING; How the Aquarium Nitrogen Cycle Works


For more information about Ichthyophthirius multifilis tomites:
Aquarium or Pond Ich: Ichthyophthirius multifilis, treatment, identification, and life cycle

Carl