As re the pH difference, I was always told that the risk of pH difference is as nothing compared to the risk of temperature difference. Plus, never ever open up the bag with fish in and then add some pond water. This is a great way to kill your fish as the ammonia reverts to the nasty form with the change in pH.

Quarantine stuff.

OK. There is one thing you need to understand fully. This is not a cheap hobby. There is a simple choice to be made, and a lot of people get it very wrong. The cheapest way in truth, is to do it right and do it properly the FIRST time. You can't do it on the cheap. Take this tank, for example. It will be big enough for now, but as soon as your fish get bigger, you will have to get something better and bigger. Fail to make it big enough then, and you will end up paying for, and setting up three versions. Investing in a good system means you have to spend less time on regular maintenance, and more just enjoying your fish.

OK, lecture over.

The bigger and better your Qtank is, the better you can treat your fish. Buy a collapsible one that is strong and good quality, and when you set it up, put it on a surface that will be warm, smooth and flat. Buy a good heater, one where the water passes thru it, and make sure it is big enough to heat the water up to 28C and keep it there easily. Arrange something to wrap around it to keep the heat in, and a cover that will keep most of the light out, and the heat in while allowing it to breathe. This also needs to guard against jumpers.

Size. Think logically here. One day you may want to treat or quarantine four fish at least two feet long, for up to two months. You want to be smug when that happens, and say "Hey, no problem!"

Biofilter. At this level there are two choices. Either just set up a brand new biofilter each time with no bacterial population, and use amquel or whatever for the ammonia and salt for the nitrite, or else arrange things so you can pull a chunk of the pond filter out and use that. (be sensible about replacing it) Mind you, you would still need to have the chems standing by in case. Setting the biofilter as a trickle tower is best, as it will cycle in record time.

My Qtreatment would be as follows. Do bear in mind this is a tad heavy, might well kill a stressed or sick fish, but will kill almost all problems they might have. My attitude is that I have to consider the well being of my pond first, and the new fish second. You could reduce it if you have a dealer you can trust, but it shouldn't be reduced too far. You will have to use your judgement here.

NO FOOD. Do not allow the water from the bag to get into your system. Float the bag in the water for 20 - 30 mins. Lift out the bag and place in box. Cut open bag, and lift fish out and into the Qtank. Dispose of bag and water well away from pond. As soon as the fish seems settled (leave it to the next day, perhaps, and keep the cover over to calm the fish) start with the following treatments.

(Note; I think dips are pointless here. They involve immersing the koi into very strong solutions for a very short period. The delicate membranes take a pounding, but the odd fluke, whatever, could survive. I prefer a longer, gentler immersion.)

Day1, Chloramine T @ 2g per 100 gallons.
Day 2 PP at 1.5 g per ton. neutralise with sodium thio (dechlor) after 4 hours
Day 9 CT as before
Day 10 CT as before
Day 11 CT as before

Day 13 PP as before.

dose with Supaverm on day 15

2 days after those doses were concluded, I would dose with Malachite Green and formalin, (day 1 and again 4 days later. (day 23)

In such close conditions, I would do some serious water changes on days 2, 3, 12, 14, 16, 17, 19, 21, 24 & 26.
just to reduce the chemicals in the water before the next dose.

Note that Qtank water if from the tap, rather than the pond, has no organics, and the PP 1.5 dose might be a bit strong, so watch out!

Make it easy on yourself,and minimise the work involved in the water changes. Only keep the minimum amount of water in the Qtank to allow the fish to swim around in, so you don't have to change the whole tankful each time, and have a container you can fill from a filtered (chlorine removal) source. I use clean pond water as I can use that for a quick fill while slowly topping up the pond. The best solution would be to have a couple of hundred gallons of treated and warmed water there ready, but that's not always easy.

Feeding. Play it by ear. Test the water regularly, and feed carefully when it's appropriate, after treatments, not before, and after the supaverm, I'd leave it at least 24 hours before feeding.

In the second phase, I would fill up the tank and start raising the temp as fast as is safe, 2 centigrade degrees in the morning and two at night, until the temp was up to 28. I'd leave it there for a week, and then drop it down to 18C at least. Wait a week and repeat. If nothing blows up, equalise the temps with the pond, and put your least favourite fish in. Ramp the temp up again twice, and if all is well, equalise with the pond and transfer them over.

That should even flush out KHV. KHV is probably the least likely thing to affect your fish, but it pays to be careful. Should your nice new purchase be carrying it, you can kiss all your fish goodbye.

Remember, throughout the quarantine, treat the fish as tho they are carrying bubonic plague. Keep a separate set of equipment for the Qtank, and never allow it near the pond, and after working with the Qtank, wash your hands thoroughly before going near the pond.

I treat sick fish differently. They go into the Qtank, and any wounds or ulcers treated at once to remove dead scales, tissue etc. The temp is raised at 4 centigrade degrees a day and salted until it is 28C and 0.6% salt. The salt needs to be added over two days minimum, possibly three. Never ramp it up too quickly. As soon as the temp is up I treat with an antibacterial. Some, like Proflavine hemisulphate require weekly redosing, which means 50% water changes. The fresh water needs to be introduced slowly so that the temp doesn't plummet. So far I have found this to be enough to treat some nasty infections, but if it doesn't appear to be working then I move onto injectible antibiotics. Azactam and amikin are favourites, but Baytril can work well too.

Anyway, I hope that helps? This isn't the only way, obviously, and other people will have their own preferences and routines for treatment. You'll develop your own as you go along.

Bear in mind that treating fish in comparatively cold water is uphill work. Heating really is the best way to go.

bil

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Jason's Q-tank schedule
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Day 1: Chloramine-T according to package instructions: 1tsp/100 gallons (3g/100g -- higher than Bil's) ALSO Disconnect external filtration, put media into bucket and add air.
Day 2: 90% water change followed by another 90% water change
Day 3: PP at 1.5ppm for 4-6 hours, stop with H2O2, halt external filtration for duration of PP, add extra O2 for duration of PP too.
Day 4: 50-70% water change
Day 5: Nothing (water change as necc for ammonia control)
Day 6: Nothing (water change as necc for ammonia control)
Day 7: PP at 1.5ppm for 4-6 hours, stop with H2O2, as on Day 3. 50-70% water change.
Day 8: Chloramine-T at 1tsp/150 gallons for 8 hours, 90% water change following treatment, followed by another 90% water change
Day 9: Nothing (water change as necc for ammonia control)
Day 10: PP at 1.5ppm for 4-6 hours, stop with H2O2, as on Day 3 & 7.
Day 11: Nothing
Day 12: MG + F at appropriate dosage (1Tbl/150 gallons for me), disconnect external filtration for first 5 hours
Day 13: 90% water change
Day 14: Nothing
Day 15: Nothing
Day 16: MG + F again for 4+ hours, followed by 90% water change
Day 17: 50% water change (try to get the last of the stuff out)
Day 17-22: add your least favorite pond fish and ramp the temp up to 28+C (80+F)
Day 27-31: let it fall back to room temp (72F or so for me in summer)
Day 32: add some ice (make the temp drop)
Day 33: add more ice (try to keep temp down)
Day 34: add more ice (try to keep temp down)
Day 35-39: ramp temp up to 28+C again
Day 42: let it drop again
Day 43+: let it drop to room temp and kick the freeloaders out to the pond! (normalize temp with pond)

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Sacramento Koi's Q-tank notes
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"Treatment program for new fish"
When water is 65 degrees or higher
(For water below 65 degrees, scroll further down this page)

When you bring in new fish it is wise to assume that they have every parasite known to man. The following has worked very well for us on new fish;

Water temperature must be 65 degrees or higher for this treatment to be effective. Salt level should be below .2% when using Formalin.
 
 

Day 1 Treat fish with "Supaverm". ( This will kill all flukes within 24 hours but not eggs.)

Day 2 Treat fish with first dose of Malachite Green and Formalin. ( If your filter is new or you suspect it is undersized for your pond you should bypass the filter media for the first 3 hours when using Malachite Green and Formalin.)

Day 5 Treat fish with a second dose of Malachite Green and Formalin.

Day 8 Perform a 25% water change and then treat a third time with Malachite Green and Formalin. (This should kill all Costia, Trichodina, Chilodinella, and most of the Ich.)
 
 

Day 9 Add a second dose of "Supaverm" and raise the salt level to .15%.

Day 10 Increase the salt level to .3%. Do not change any water for the next 10 days. If you suspect or see any anchor worms or fish lice you can add Dimilin at this point. One treatment of Dimilin is usually enough.

This last treatment of salt and "Supaverm" is to kill any fluke eggs that may have survived the original "Supaverm" treatment and to kill any Ich that might be left. Ich has a long life cycle. Leaving the salt in for 10 days after the Malachite Green and Formalin treatment should break that cycle. Ich is easily killed with salt.

A good reason to follow the treatment for the full three weeks is due to the possibility of exposure to the "gill virus". The virus seems to become active when fish are stressed and will usually kill the fish within two weeks. Shipping fish is very stressful to them. If after three weeks you have suffered no fish losses you probably do not have a problem with the virus.
 
 

"Treatment program for new fish"
When water is below 65 degrees.
 

When you bring in new fish it is wise to assume that they have every parasite known to man. The following has worked very well for us on new fish when the water is below 65 degrees.

Potassium permanganate treatment

Day 1 Bypass biological filter media. Potassium permanganate will kill the bacteria in your filter if allowed to flow through it. Make sure there is plenty of water flow and aeration during this whole procedure. This procedure will consume large amounts of oxygen and can suffocate your fish if sufficient oxygen is not available.

Add 1 level teaspoon for every 600 gallons of water in the pond. The water will turn pink in color. This pink color means it is active. When the water changes to a tea color, the potassium permanganate is no longer active. At this point you can resume filtration. To clear up your pond water add standard 3% Hydrogen Peroxide at the rate of 1 quart per 5000 gallons of pond water. This first treatment will probably only stay purple for less than one hour. Note: You must wait 3 days between treatments for the Hydrogen Peroxide to evaporate or it will neutralize the next potassium permanganate treatment and leave it useless.

Day 5 Repeat all the above steps again. Do not forget to bypass your filter. This treatment should stay purple longer because the organic material in the pond is being consumed.

Day 9 Repeat all the above steps again.

Continue the above procedure until the water stays pink ( champagne color ) for at least 8 hours. This usually takes about 5 treatments. When it reaches 8 hours, neutralize water with Hydrogen Peroxide and do a 50% water change. Your fish should now be free all of parasites.

Hint: #1 - Scoop up some of the pond water into a white ceramic cup. It is much easier to determine the color of the water against the white background.

#2 - In a very clean pond or treatment tank I would reduce the dose from one level teaspoon per 600 gallons to one level teaspoon per 800 gallons.