I have a sick Koi. I apologise for the length of this, but I wanted to provide as much information to all of you as possible. I have owned the pond and fish for 4 years (it pre-dated my ownership). I don’t have a microscope, although I’m now determined to get one. My husband’s a lab technician, so he can likely handle a microscope better than I.
Overview of affected Koi: 26” female Koi (garden variety domestic), 11 years old, small bulge on body right side (more toward the caudal fin from centre side of fish – it looks like every sample I’ve seen online of an ovarian tumour). Always had a hearty appetite, always been a very healthy fish. Damage to right pectoral fin and lower caudal fin from rubbing herself aggressively against stationary objects in the shallow of the pond (I watched her do it). Left pectoral fin has two splits in it (run parallel to the cartilage in the fin), but no redness or fraying evident – there was initial one split, the other appeared yesterday. Two weeks ago, she began surfacing on her side (head up, tail down), circling frantically; then she’d rest on the bottom for a while, dart frantically across the pond wriggling her body dramatically (not side-swimming flashing, but twisting her head going hard left, hard right, like she’s dancing the twist), surface, and repeat. Always the right side that surfaces, if that’s remarkable.
Pond overview: Current temperature: mid-day 72F / early morning 64F. 8’ deep at the drain, 10,567 USG to the high water mark. Matala and Kaldnes filtration (8 cubic feet of Kaldnes) + 80W UV, pump circulating 5,500 USG/hour; 26 Koi (2 @ 26”, the rest are their offspring – 16 inches or less in size). Fish winter under ice, and the pond is normally clear of ice and into the low 50F range by mid to late April.
Water parameters as of yesterday 6:00 p.m.:
Well water filled (no chlorine)
Water temperature: 72F
PH 8 – 8.2 (static)
Ammonia < 0.25 ppm
Nitrite < 0.25 ppm
Nitrate < 5 ppm
KH 140 mg/L
GH 180 mg/L
Iron 0 (reading same for both non-chelated and chelated iron)
Generous aeration
Koizyme was added in the spring for 6 weeks
Aquascape Pond and Debris clarifier was used in the spring – 2 x 40% water changes have been done since then (one as soon as the ice was off the pond the week of April 15th, and the other this past Monday).
Salt 0.2% to protect against Nitrite/Ammonia, since where I live, the biological filter is just now establishing itself (hence the elevations in ammonia/nitrite/nitrate; normally, they're undetectable). I just cleaned and re-potted pond plants this week, so the Nitrate should begin to come down. Her issues precede the plant repotting; pond is vacuumed – there’s no debris in the pond. The only difference in water parameters between now and two weeks ago was that ammonia, nitrite, and nitrate were undetectable.
Additional information: no other Koi is flashing or showing any of these symptoms. There is a Painted Turtle in the pond – we live in a wooded area, and she arrives annually. I imagine turtles can bring issues to the pond, but I can’t really prevent this, since we live in a protected wetland area, so I’m not allowed to disrupt their habitat. The Painted Turtle shows no aggression towards the fish; in fact, it often scurries under objects to avoid the fish, who are often in hot pursuit. She goes in and out of the pond once daily, lays eggs in the area for a few weeks and then disappears back into the forest.
Treatment of the sick Koi to date:
Assumed she may have a gill fluke – or that it was the onset of a fluke problem – so I treated the pond with Praziquantel, 120% dose. A couple of other fish did ONE minor flash within the first hour of treatment, but otherwise, there’s been no significant reaction from fish in the pond. After 24 hours, she showed absolutely no improvement. I think the prazi treatment may have been pointless. I removed her after 24 hours, did a PP dip at 100 ppm for 5 minutes (no signs of distress from her whatsoever), then rinsed her in clear water, then placed her into a hospital tank. Added salt in increments to 0.6%, lots of aeration, increased temperature in increments to 80F, added Melafix to help with abrasions to fins. Injured fins were red and vein-ish, but not to the base, and not a dark solid red. No ulceration present, no signs of mouth irritation/rot, no white or red spots on her to indicate any issue whatsoever.
Progress: After 2 weeks in the hospital tank, frayed pectoral and caudal fins have repaired significantly, but although she rests quietly and will swim normally in the hospital tank when I interact with her, she won’t eat, and she’s normally eats quite a bit. Tried returning her to the pond yesterday with the hope that she would return to normal and eat in the pond environment – ensured the water parameters, temperature, and salt were very close or equivalent between the tank and the pond: she immediately began the same behaviour! It’s as if she wants out of the pond immediately: circling at the surface, then down to the bottom to rest, then wriggle all the way back to the surface and circle frantically. Removed her, returned her to the hospital tank, now increasing salt incrementally to 0.6%, added Melafix, increased water temperature incrementally. She still won’t eat. Swimming behaviour is normal in the tank, but becomes completely abnormal in the pond.
I don’t have a submersible pump, or anything electrical in the pond, so I have ruled out a short as a potential cause.
At this point, I’m considering treating her with Tricide-Neo for a bacterial infection, and if I can get her to eat, Romet-TC. I’m not optimistic I can get her to eat. She won’t even eat peas or fruit at this point.
I’d appreciate any advice or direction you may offer – I really don’t know if I’ve overlooked anything, or if I’m on the wrong track and wasting precious time, given she’s not eaten for almost 2 weeks. I don’t know if it’s possible that she could have any parasite or fluke after the PP dip I did, albeit I did the dip only once. Should I repeat a PP dip daily for 3 or 4 days?
The closest fish vet is 100 miles (160 km) away, and although he’s mobile, I’m not sure he’ll drive this distance to administer an injectable antibiotic. I’d likely have to transport her to and from the vet.
I am wondering if: (1) she may have an object lodged in her mouth or gill, although her mouth and gills appear to be acting normally, so I haven't looked; (2) this may be something that happens in fish that have a tumour?
I can post photos/video (or share them otherwise). I thought I’d start with this overview. I really want to do everything I can for her, but I am a novice to this hobby, so I'm looking for help and knowledge.
Many thanks in advance,
Hillary