|We have had our large pond for about six years. We have a bio filter and a UV light. This week was the first time we ever lost a fish. We have no goldfish, only Koi. The koi spawn every year and we remove the babies. I missed three last year. This year, one of the babies showed up sick. He had a slime all over him. It looked like it was hanging off of him a little bit, there was so much. Some of the slimey coating had a beige color to it.
None of my fish has any other symptom. This is the only affected fish. I have been using Program on the fish over time.
Would Koizyme help my situation? Do I need to feed them a medicated food?
What you're describing is a fish with pretty severe immune suppression which allowed either Epistylis or Saprolegnia to infest it. Baby fish are more sensitive than other fish and I'd be highly encouraged that it was only one fish, and no other fish have symptoms.
So, what to do for the other fish.
Water testing. (Ammonia, nitrite, nitrate, pH and carbonate alkalinity.)
The most important tests among the above, are all of them. Ha! What you're trying to do is determine if there is a stressor in terms of water chemistry in their home.
We KNOW that this last winter's cold was a factor, a "given" if you will.
Koizyme is not a bad idea at all. Do it AFTER a major water change with dechlorinator.
Low level salting would also be a good, safe step.
Finally, breaking the winter's fast with medicated food wouldn't be a bad idea.
See, this case is interesting because you only had ONE fish affected. So it's not a good idea to barrage the fish with a million caustic medications when only one fish had a symptom and everybody else seems fine.
So you have the water testing to do in order to determine what pushed the one little fish into illness.
Then everything else you do should be SAFE, STRESSLESS, and PROPHYLACTIC.
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