Midwest Pond and Koi Society - Q&A #146 - Flashing fish; how to get rid of koi parasites

We have an approximate 4000gal. pond in the yard. Our Koi this spring are flashing. They began flashing in the fall. We treated with Proform C for 3 days in the fall. We treated again just this past week on the 2 warmer days, when, the water temp. was in the 50's. They still are flashing, and, we noticed some have bloody streaking in the tails. How can we get rid of the parasites, and, clear up the tails?

Should we use potassium permanganate, and, in what dosage? Or should we use something like Pond Fungus Eliminator or Melafix? We do not want a problem this Spring. We lost almost all of our Koi about 2 years ago. They have rebounded and reproduced and are quite large now. We have water lilies in the pond.

Should we use salt? The 2 years ago, when, we lost 16 of our Koi, we had Dr. Chris Shirkey out about 3 times and were injecting all of our Koi with Amikacin intramuscular (we still lost 16, only 6 survived). We do not want to go thru this again. Please help. We now have over 30 Koi.

We run 5 filters on this pond now. Water quality is good. We try and keep up with water changes, but, we've been not regular with this in the winter months. We would like the Koi to stop reproducing, because, we keep buying them more filters. We would like to give some away, but, they are large, and, we do not know how to give them away. (We do not want to euthanize, we would like to give them homes) Please give us some advice. We do have Doitsu Koi in the pond also.

Dear Nancy,
In all probability, your fish were flashing early on because of built-up ammonia and dissolved organics accumulated over the winter when your filter bacteria were inactive and your water-change schedule was either restricted or non-existent. While 30-plus fish in 4000 gallons is doable over the winter when you are not feeding, it is still a considerable load and needs careful management.

Your present problems are less likely to be parasites and more likely due to the fact that your water is too cold to use Proform-C safely. The streaking in the fins is a sign of stress, usually associated with poor water conditions or chemical pollution.

Proform-C is a mixture of formaldehyde and malachite green, and should not be used until water temperatures are consistently in the 60-70 degree range, with the emphasis on consistently. You'll need to do repeated 30% water changes daily, pre-treating with dechlorinator (Stress-X or similar)and trying not to alter the ambient water temperature too drastically, over the next week or two to get the chemicals out. Only after the Proform-C is mostly gone can you safely begin to bring salt levels slowly up to about 2.5 pounds per 100 gallons. Holding that level for a week or two will take care of most residual parasite load; I'd then allow the level to reduce slowly down as the water temperature rises with routine water changes.

Water lilies are no problem as long as the higher salt levels exist at a time before they begin to sprout in the spring. They tolerate salt levels of 1.5 lbs/100 gallons well (1.88ppt).

There is no way you can stop your koi from spawning, but new homes for them are not that much of a problem if you are a Club member. Bag them up and bring them to the fish auction .

As far as water quality goes, I expect that you are testing ammonia and nitrite. Are you also testing pH and Alkalinity? Are you adding fresh tap water without using a dechlorinator? Remember that Chicago-area tap water is heavily pre-treated before it hits our faucets, and chlorine and chloramine will kill your fish just as fast as parasites.