Virkon Aquatic to treat really really bad bacterial issue - saved near dead koi
Hi all
New to the forum – so please allow me to do a quick (albeit a long one!) self-intro.
***The main purpose of this post is to see if the more experienced koi keepers on this forum have used Virkon to prevent/treat bacteria issue – and if so what was your experience with Virkon***
Back in Dec 2020 we moved into a new property and I inherited a tiny 150 gallons ‘pond’ in the garden – which is effectively a galvanised steel (all rusted over inside) trough buried completely, with the top flush with patio surface. It had a few goldfish and x2 mature green tench in it, and very basic pressurised filter.
First mistake I made was cleaning the ‘trough’ by removing all plants and didn’t put them back in after finished – next morning all the nice coloured goldfish were gone (I’ve seen seagulls and crows around) – all left were 1 blue shub and the x2 green tench (impossible for predators to get them in the murky water)… So I put a mesh cover on, then bought/added my 1st Koi – a tosai Kohaku import from Japan. That was in cold January 2021.
Second mistake I made was start feeding the Kohaku immediately without knowing water temp and testing water etc… It eagerly ate each and every time food was offered, as was the shub (the tench cleverly refused food and sat on the bottom) – within 4 weeks the Kohaku had clamped fins and swimming strangely – next morning I found it stuck between a planter and the pond (trough) wall with head down – it was still alive when I freed it but eyes badly sunken and died shortly after. Buried in the garden with my young daughter who loved it to bits and was very upset…
I then bought/added 1 tosai Karashigoi and 1 tosai ghost – these guys darted around the (rusted) trough/pond like crazy and bumped into sharp/rough surfaces and got nicks in the mouth/body area. I asked the dealer who sold me these who said no big deal just ‘observe’ and no need to treat. Within a week these nicks turned into infections and the Karashigoi’s mouth started to rot. The ghost had bleeding around some scales – the dealer told me ‘no big deal as ghosts are very tough’… Despite this bad advice I gave them regular salt dips but the combination of poor water quality (which I only just realised later on) and poor netting resulted in these two fish getting worst. I did start testing water at this point but only with strips.
So a few months ago I persuaded my wife to let me put in a gigantic (in her words) 2000 litre vat in our garden and moved the fish there, while I carefully consider if I want to fill the trough/pond before I kill more fish, or expand it and take this on as a serious hobby. I also gave away the two green tench. So only 1 shub, 1 ulcerated Karashigoi tosai, and 1 ulcerated ghost tosai in the 2000 litre vat. I also upgraded to a second hand Oase Biotec 5,1 filter, with added improvisation of poly wadding sheet over the outflet (to remove fines), plus I stuffed the 1 meter 3” outfletpipe with Sera Siporax media (which is said to offer x30 times more surface area for bacterial to colonise on).
Sadly by this time the Karashigoi and ghost’s ulcers got worse. I gave the vat a 4ppm PP dose, repeated every 3 days for 3 times – at this point the water got a lot clearer – but the ulcerated kois continue to deteriorate.
I then started Tricide Neo treatment (important from US to UK) – daily dips followed by a light sprinkle of dry TN powder and dental powder/propolis. At this point both the karashigoi and the ghost had developed multiple ulcers – some as big as 50p coin showing bare muscle. TN was not enough to save the ghost and it developed heavy fungus (at which point I moved it to a 100 litre bowl as a temp QT, with an airstone and salted to 0.8%, with twice 50% water changes per day) sadly it died within a week.
I was almost certain the karashigoi would soon follow the path of the ghost and kick the bucket – other than the mouth rot which was getting worse, 50% of its belly was showing red through, and on one side it had a 20p coin size bare muscle ulcer, on the other side a 50p coin size bare muscle ulcer… I was fully prepared to see it die any time in fact I dug a hole for it in the garden already – next to where the Kohaku and the ghost were buried! I stopped Tricide Neo for it after using almost the entire 110 grams pack which was quite expensive.
It was at this point, I read about Virkon Aquatic – and I put in a treble dose to start with (x3 5 gram tablets in my 2000 litre vat), after cleaning the filter and siphoning the vat bottom clear. I thought I’d either kill the karashigoi with this strong dose, or it may do some miracle… On the same day (a few hours after putting in Virkon dose) I added x2 large golden tench (20 inch plus size) and x1 red karashigoi tosai – I was thinking the yellow (ulcerated) karashigoi would certainly be a goner, and the red karashigoi would be my LAST ATTEMPT to keep koi – if it ends up dying as well, I’d only keep golden tench!! (The blue shub was still healthy as ever after all these PP / Virkon treatment!).
A miracle did happen – the ulcerated karashigoi did not die from Virkon, and the new golden tench seemed quite happy and settled in, as with the new red karashigoi – all three new fish I didn’t even bother to QT before adding to the vat. In 3 days time I repeated Virkon treatment with standard dose (x1 5gram tablet in 2000 litre water), and I did this for 2 weeks (twice per week treatment). Each and every morning I expected to wake up to see a floating dead yellow karashigoi – but that fish just survived each and every day, and it was actually thriving… I could see the previous 20p coin size ulcer healing over with white film on top, but I couldn’t see the larger 50p coin size ulcer which is near its bottom – so out of curiosity I netted it and unbelievably it closed to a much smaller size!
I have to add, when this ‘miracle’ happened, or roughly when I started Virkon treatment – it coincided with the weather warming in July and water temperature rising to 20degrees. Then the mini heat wave came and water temp went to 25 degrees. I was finally certain that the yellow karashigoi would go on to survive.
So I thought I’d better start doing this more seriously – so I started testing water with drip kit – pretty stable readings every day for the past 3~4 weeks – 0 ammonia, 0.25 nitrite (if I don’t feed for 1 day it goes to zero), 40 nitrate. I maintain KH to 8 drops by occasionally adding bicarb.
I still treat with Virkon once per week. More importantly I clean the filter twice a week and if I can see poop on the corners of the bottom of the vat I siphone it out.
So I now have x2 20” plus golden tench, x1 8 inch blue shub, and x1 yellow karashigoi (the one that survived from the ulcer) and x1 red karashigoi – both grown to 10” plus now – in my small 2000 litre vat – with good water test readings.
This coming autumn/winter I’ll dig out that buried galvanised steel trough and dig a proper pond of about 5000~10000 litres (the max size my family would permit me building in our garden).
That’s the end of my long intro and bad experience / steep learning curve!
One last thing I’d add is – I discovered after adding a standard dose of Virkon my pond water would test pink using DPD4 tablet – the pinkness would disappear in less than 30mins time. This prompted me to look at the Virkon lable and it says it has active chlorine ingredient. I do wonder if this is the same chlorine as in tap water and if it could cause gill damage? I’ve asked Brandon Biosecurity this question from whom I bought the Virkon tablets, but was told their vet is currently on holiday so I weren’t get an answer till a few weeks later.
Thank you for reading my long intro post – I’ve learned so much browsing this forum for the past 6 months or so – and have been meaning to post my learning experience for a few weeks – only have the time to do so now.
Interesting story and thanks for sharing.
I've used Virkon for occasional "clean up" of the water but I've not had a need to treat for bacterial issues so I don't
have any experience with it for that.
It sounds like you already have seen this, but I'd treat Virkon as a treatment and not a "band aid" for the poor water quality
and longer term you should try to improve the conditions in the pond as opposed to trying to use Virkon on a regular basis.
Sorry, I can't help with the chlorine type as I'm on a private well and never had to deal with chlorine or chloramine.
I hope you'll share what the vet says when they return.
Here's a past discussion on Virkon that might be of interest too:
Thank you very much Steve for that informative thread.
I put in a weekly standard dose this morning - unlike previously, I did not do water change and Virkon on the same day this time - I did water change the day before, as I suspected the residue ST/dechlor might have interfered with Virkon effectiveness for my previous doses - as the DPD4 tablet test went from pink to no colour very quickly within 30mins.
So yesterday I did a 20% water change and put in 'just the right amount' of dechlor - unlike before I would put in a bit 'extra'.
This morning I tested the pond water first with DPD4 and there was no pink colour.
After putting in the Virkon dose, I first took samples every 10mins for the initial 30mins and tested with DPD4 - they look like this - left most was the 1st sample:
Seeing almost the same pinkess between 10 and 30mins, I then sampled the water every 30mins - they look like this - left most being the sample took first. Interestingly, after 2hrs (after collecting all 4 samples), the previous 3 samples almost showed no pink colour testing with DPD4. Only the most recent sample showed pink as it was tested immediately.:
I then sampled/tested every hour - at about 5hrs mark, the sample showed almost no pink colour.
This is very interesting - as the instructions I got from the vendor (Brandon Biosecurity in UK) says 'turn UV off before dosing', and 'turn UV back on after 6hrs'. So I am guessing, either 1) the active chlorine ingredient somehow gets inactivated (could be by another slower release component of Virkon), or 2) the trace residual ST in my water slowly inactivated the active chlorine in Virkon.
This is under the big assumption that DPD4 tablet tested pink = chlorine in water. As Virkon tablet also has a pink hue which disappears gradually as the dosage loses effectives after a few hours (according to https://www.fishersci.co.uk/webfiles...cs/SLSGD05.PDF )
Anyway, hope this small test may be helpful to others who may choose to use Virkon to disinfect water to sort out bacterial issue - from what I have tested, ST content in water will instantly deactivate some component of Virkon - so probably best not to do a big water change 2~3 days before dosing Virkon - just like PP.
I forgot to update last time, but the problem didn't get better for a few days so I put some gentian violet on it and that solved it. Now I'm having the same thing but worse on one of my kohaku, so I'll try Virkon first again and see.
Based on the label, it looks like it's mainly potassium peroxymonosulfate, I looked it up, it's an oxidizing agent, I guess similar to PP.
I would actually suggest using oxolinic acid at 0.5ppm and continous treat the fish for 7-10 days, it's an antibiotic and should work for internal infection issues.