I'm having a problem with gill flukes. Well, not me, but my Doitsu Showa is (ha).
Here's the backdrop. I had some water quality issues this spring - a filter crash, and too much muck in the pond. In very early summer, I added an Aquadyne 8000 bead filter & UV sterilizer to my 3000 gallon pond and the pond health has improved dramatically - less muck, very clear water, no leftover koi waste to cause problems. But during this unhealthy spring period, my Doitsu Showa got sick and i've been nursing him back to health all summer.
About 10 weeks ago, i discovered that my prize Doitsu Showa had a very bad case of gill flukes. I did two back to back treatments with AquaCura, a powder prazi product, and he started eating again and resumed normal behavior. Then, about a week to 10 days after these first two treatments, he got sluggish again and ate sparingly - so i did another prazi treatment, and he perked right up and joined the other fish in being very active and hungry. This pattern has repeated itself over the summer and today, i just did my 6th prazi treatment since late spring! The other fish are super active and are feeding voraciously - and i think of this doitsu showa as the weakest fish (health-wise) and the first to exhibit symptoms - so in that sense, he's the "canary in the coal mine".
I've read that gill flukes are notoriously hard to get rid of - is this accurate? And if yes, are there any tips for ways to improve treatment? My pattern has been this: treat for 5-7 days (with the UV clarifier off), do a water change, wait exactly four days so more fluke eggs can hatch, and then do the second treatment. Then about 7-10 days after this process is finished the Showa gets sluggish again, etc.
Finally, my knowledge and koi skills have improved dramatically in 2020 - but i'm still not ready to get a microscope and start scraping. I diagnosed the gill flukes just based on symptoms alone - isolation from the other fish, hanging near the aeration sources in the pond, not eating, etc.
SETUP: 3000 gallon pond w/a small mechanical biofall, a bog filter, and now an Aquadyne 8000 bead filter with UV clarifier.
Water quality is terrific - zeros across the board, with KH at 12 drops, PH about 8.1.
Thanks in advance for your insights! ck