Koi with bad reaction from eating prawns

[KiOgon]

I'm hoping for some advice please. 6 of the 9 fish in my pond are over 21 years old. 1 of these, a Kohaku with Shimmies or a 'manky Sanke', was very greedy at the regular prawn treat time and seemed to react badly straight after -- shaking his head and darting around, erratic behaviour, his shiro is very pink and around his eyes and back of gill covers look inflamed. Water tests with Hanna meters;

ph 7.4, temp.19.5, KH 38, NO2 0.03, NH3 0.08. We have tried a salt bath at 0.3% for 30mins + another 30mins at 0.6%. Some of the other fish are also a bit pink with ocasional flashing but nowhere near as bad.

I don't believe there is any parasites involved as the reaction was instant after the feeding, I have a microscope and have taken scrapes many years ago, but my disabilities are limiting and I rely on my son for help when he visits on a Sunday.

We are convinced the prawns have started something but have no idea what is the best course of action/treatment. What can you suggest please?

[davethefish1]

gill flukes go nuts when a koi is eating,
stretching and contracting and catching fine particles of food as they travel through the gills.
thats why they often flash after feeding.

unless a piece of food has got stuck in his gill rakers, and normally there is no flashing and erratic behaviour.

always after water tests prove ok, scrapes are needed can you get your son to pop round and do some?

[KiOgon]

Thanks for that Dave, I'll see what we can do.

[g mac]

I've seen the same behaviour with mine and it was Gill flukes.

[KiOgon]

Thanks Gary, I was hoping it was just the prawns

[RS2OOO]

Assume prawns are a food the Kohaku is familiar with and has had before?

Could the prawn have been contaminated with a tough piece of shell that has got stuck somewhere in the mouth or gills? (Had this before with prawns that I ate, and suddenly felt immense pain, initially thinking I'd broken a tooth before realising there was a really hard piece of shell embedded in the prawn).

[KiOgon]

Yes, they've had defrosted/cooked frozen prawns frequently over the years, this year more than ever as I've been getting 1/2 price offers and stocking up the freezer, we've been eating them too so know they're OK.

They look forward to their afternoon treat, sometimes queuing up for hand feeding, I cut the big prawns up into bite size chunks of course Mussels Squid Prawns Banana.jpg this was a mixed treat