Costia :(



So, we’re wondering why the koi are dying off at a very fast rate now, where they did perk up. Defo Costia,

Trying to get hold of someone to speak to now. Maurice or Dennis anyone!!! this is desperate. There are thousands of them. Unmistakable bastards.

I need something fast.

Still getting the nitrite out, but this is killing all my fish!!!!



Thanks for the reply,

Seeing as my pond has salt in it, I can’t use FMG.

Decision is made.

After speaking to some Top blokes. (One from here) I am going with pp. I’ve made the decision seeing as I am losing them so fast to hit them tonight and re
dose as required.

We’ve been doing major water changes because of the raised Nitrite and Ammonia levels, so the salt will have been diluted if not a lot, but at least by some, 6-10 inch a day sometimes twice, so I’m hopeful.

Preparing 3g of pp in hot water as we speak. There are a few koi I know won’t make it through this, as they’re already suffering, but I have to give it a go. Chances are by morning even more will be dead.

We’ve lost 14 up to now, there are still 60 koi worth giving it a go for.

Will post in a little while and fingers crossed

Having a microscope is THE BEST peace of equipment you could ever have. Every koi keeper should have one.

Will post a video of them later, they’re still scooting all around the slide as we speak some 30 mins later.

How hardy are they….


Thanks Dave,

We can’t be online all the time. Lucky for me, I do know a couple of great guys and can phone them up. One phoned me (Al) thanks so much for that…

Here is the video I took, not great, but couldn’t find the holder thingy for it. So it jitters a bit.

Costia – YouTube

so of course, anyone who would like to confirm my diagnosis please do. I was a little unsure, but it is pretty un mistakable.

Nearly the last bit of pp in. Looks like 3 more on their way out.

The others sort of swimming about, the odd one has a bit of a run about, I would guess that might be the costia putting up a fight.

Would a bad reaction to PP be them floating or hiding. Hard to see them in dark purple water!


I am not a dumbo them, thanks. Yeah no one is trying to jump out.

Just put the nets in like you said, and they’re actually curious, daft fish. I will lose a couple more, two really struggling, floating. but the others seem okay swimming about, almost last bit in. So it prob is a pretty high dose of pp, but fingers crossed anyway.

If the net drying out still has live costia on, then I am going to have to fill the tank, because there still could be some in the algae around the sides or in the corners, so the aim for in a couple of days would be to have a full tank and dose again.

Fingers crossed, as at the higher temp they’re breeding like mad. Do you think I could drop it back down a little? Or keep it as it is, stable and ready for healing?


I don’t know the answer to that one. Will keep it as it is for a day and see if the pp makes them more like my fish.

I guess then will come a lot of healing anyway, as looking at some costia can be a nasty nasty parasite leaving open sores etc.

Last dose went in, fished the two dead un’s out. that makes 16. But I have high hopes now.

The costia bug we had was resistant to high levels of salt. Salt just doesn’t kill things anymore, shame, it used to be so good.

Will keep you updated.

Thanks so much once again. I owe you more than a few cups of tea now, Al….


Well had to Hp as a fair few looked like they were struggling more for 02, so the pp was in for 90 mins, will see how they’re looking in the morning, best to leave them alone I think to recoup. Set the temp a little lower as it had dropped anyway, don’t want a swing in it worse than the ph.

I will catch one and take a look tomorrow, there are a few with patches where the costia I imagine is ripe, from research it seems the ‘lesions’ are worst parts… will keep you up to date.

Thanks everyone for stopping by and fingers crossed there are a few survivors.

(After all the two jap koi are still swimming about happy as larry)

Speak soon




This morning, fish looking better, but still hanging about under the backi shower.

No losses.

Will report later.

Thanks everyone, fingers crossed we can deal with any secondary stuff as it pops up now, and hopefully after a second dose of pp, the costia will be dead.


Well, we lost one today. A silver and orange one. But for the most part the other fish are swimming about, not gasping at the surface. To see them all I have to remove the air stones, and there were a couple layered ontop of each other hiding on the bottom. Not looking too happy.

Should I catch one, take a scrape and see how the pp worked?

Temp is 27,

Ammonia and Nitrite back to 0, thankfully. Although I really want to see if they’ll eat, I’m just not sure I should.

I have some sansai biorex and clay to help them if anyone thinks it is worth popping some in?

I guess it is a bit of a waiting game to see how they really do. I think they’ll need another hit of pp on Thursday, been 24 hours. its just a horrible waiting game.

Also worried about the big guys in the main pond, but I’ll give them a couple of days they dont seem to be acting up…



5.59 am

News this morning.

They’re still sulking and hiding. But no deaths in 24 hours

If water is okay later, I am going to drop a little medicated food in. The Asagi and Kohaku are actively looking for food and as soon as the flap to the polly tunnel opens they’re there nosing.

Fingers crossed and will redose tomorrow.

Everyone in the main pond acting like normal, fighting for food this morning.

I can hope we’ve turned a corner and finally luck is on our side.

Will let you know later how they’re doing though.


Hey there,

So today managed a scrape on a pretty poorly koi, Still a bazillion costia.

Not good, going to have to re-treat tomorrow for sure.


Hi there,

I could spot Costia at 160 quite easily. I’ve only got a 5x and 16x eye pieces, and the mag on the scope itself is 4x 10x and 40.

So using the 16x eye piece and the 10x scope mag I get the 160, I did try the 5x 40 which gave me 200 as well, and they’re still easy.

I am guessing this is because there were just so many of them. It might be hard to spot one or two not sure, I’ll let you know if I can shift the blighters.

Hope this helps you

7.35 pm

For the first hit, I was just trying to get as many of them dead as I could. But the koi were really struggling, so I only managed 90 mins.

I have a course of treatment to follow tomorrow, so I guess I’ll have to give that a go.

How did you end up with Trich after Costia, wouldn’t the pp the first few time have gotten rid of this?

nightmare for you too

By kanundra Posted in Koi

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