My 1,000 gallon pond has great oxygenation, great flow turnover, and according to the fish store that tested my water, everything is perfect, although the pH is at least 8 (his kit only went up to 8). I do 10% water changes a week, with dechlorinator. Water is crystal-clear, and I have a UV light running. I have 8 goldfish that are happy and have actually had babies. There are several water plants. All in all, should be perfect. I bought three 5" koi from Petco on May 7. Two died within a week. Replaced them with 4 domestic koi from a koi dealer in San Diego (1 4" and two 3" ones). About a week later, put in 3 more. Then on May 26, put in another 2 more 5" koi. Within two weeks or so of putting the first batch in from the koi dealer in, 2 of the first three domestic koi died. Then 2 of the next three died, again within about 2 weeks of putting them in. Now, I have 1 5" koi from Petco remaining, 1 5" from the next batch, and the 2 that I put in on May 27. The ones from the koi dealer that I saw die looked fine, then started swimming lethargically, barely moving when prodded, and were dead within hours of that behavior. There were no overt problems observed on any of the dead koi, either in the gills, fins or body. The remaining 3 koi sit on the bottom all day, unless I poke at them and then they swim fine, to another shaded area and stay on the bottom (about 18" deep). They appear healthy. The goldfish continue to do fine. My koi dealer said that maybe I had KHV from the Petco koi. A fish dealer looked at one that had died that day and said that it looked normal.

The koi dealer said to salt the pond. I don't want to kill the plants, though. I also read online that sitting on the bottom all day may be indicative of flukes. But wouldn't flukes also affect the goldfish? Anyway, what the heck should I do? I don't want to put more koi in until I figure out what's going on, and its coming on two weeks for the two that I put in last. Nobody seems to be able to tell me what to do, and its not worth getting the dead koi tested for KHV.

I am sure Robyn can help you. But in the meantime, try this website. Good Luck.

http://www.fishdoc.co.uk/

PS. Shouldn't the pH be 7?

I'm sorry about your new koi. Why would they die and not the goldfish? It could be that the koi carry some disease that was more advanced on them and might eventually get to the goldfish. It could be that the koi were too beat up or unhealthy when you got them although it sounds like they're fine. It could be that the koi have something that goldfish don't get like the KHV. It could be that the koi died because they are more sensitive to certain things than goldfish such as low oxygen.

Your pond pH should ideally be between 7 and 8. If it's much above 8, you need to figure out why and try to bring it down. I suggest getting an accurate reading of the pH. The store only tested for certain things. What did they test for? Ideally, you would test for pH, hardness, alkalinity, ammonia, nitrite, nitrate, and oxygen levels to start with when a problem is afoot. What kind of filtration and aeration do you have?

Check out this web page:
http://www.koivet.com/

There are pages on that site about Koi Herpes Virus such as http://koivet.com/html/articles/articles_r...search_term=KHV
If you suspect KHV, it might make sense to take the koi out and heat them to 87 degrees F to kill the virus. I am not sure if the entire pond has to be heated, if the virus is in the water or carried by goldfish. The site probably tells you somewhere. If it's KHV, you can expect to lose the rest of the koi eventually.

You may not be able to have the koi tested by an official lab but I do suggest contacting your local koi club. They will often come out and put the fish scrapings under a microscope and be able to diagnose many of the basic problems that koi can have.

Koi experts say to have 1000 gallons for the first koi and 100 gallons or more for each additional koi. So, in the end, I suggest onyl keeping a few koi in your pond anyway. I wouldn't add any more koi. If your three survive, hopefully, they will be plenty.

Sitting on the bottom (lethargy) can be a symptom of almost any parasites, bacteria, fungus, virus, etc. They could have gill or skin flukes. Flukes would also infect the goldfish.

Adding salt to the pond helps with my parasites, bacteria, funguses, etc. but not viruses. If you have plants, keep the salt concentration below 0.05%, or the plants will start to yellow and die. In a plant-free pond, 0.1% salt can be used.

I suggest trying to contact your local koi club for help (to look at scrapings of the fish under a microscope which will tell you if they have flukes, etc.), testing the water for a wider range of things, continuing with partial water changes, filtering and aerating the water well, adding some pond salt and maybe some MelaFix, adding parasitic killer only if that problem is verified (or pretty likely; parasitic medications can kill good bacteria, sometimes tadpoles, snails, insects, weak fish, etc.), and waiting.

I hope things improve!

Is your pond new? What's it constructed out of? By chance is it concrete?

The reason I ask is because my Uncle built a concrete pond embedded with red rock. Basically did a rinse, fill and added Koi (no goldfish). He had very similar problems the first year with Koi dying (total loss), not acting right (lethargic), and staying at the bottom.

He just kept replacing them. It was never determined what the cause was. I always thought it may be chemicals leaching from the concrete, or the red rock that test kits don't pick up.

Again, considering your fish illness description is very much the same as my Uncle; makes me wonder.

My pond is a liner pond, full of plants. Testing of the water showed low ammonia, nitrites, nitrates, higher pH (8+), water quality is generally excellent. I hate to salt the pond, as I am told that the concentration required (.3%+) will harm my plants (about $450, although I could put all of the plants in a large vat and then salt the pond, I guess). Sad truth is that the remaining koi are $15 each. To run around testing everything, setting up a quarantine tank, buying medicine, having the fish tested, all of that is so expensive. I am wondering if I should let the remaining koi die (although I hate to), drain the pond, and put the goldfish back in. But if it is flukes or something like that, wouldn't the goldfish also be affected or does it just hit the koi? I am also thinking of putting the remaining koi in a small tank, and salt the tank and see what happens. If they perk up, who knows? Maybe I can even try heating the tank in the event that it is KHV, although that is not a proven cure, from what I understand. Is there any way of diagnosing parasites in the dead ones? I vacuum-sealed each one and put each in the refrigerator in the meat storage area, which is just above freezing. A friend who is a biologist for the state said that parasites do not survive in the water, but can in the sediments. Is there some way to check that?

You definitely want to get the pH of the pond below (or at) a pH of 8.

For ponds without plants (or snails, crustaceans, insect larvae, etc.), you would use 0.1% salt. For ponds with plants, use 0.05%. A concentration of 0.3% is a lot and would stress the fish.

If the koi do have parasites, the goldfish will get them too eventually. The goldfish may be able to fight off the parasites better than the new, stressed koi.

If you can spare the time and effort to put the remaining koi in a quarantine setup with 0.1% salt and maybe heat it, that would be a good idea. From what I've read, heating the fish to kill the KHV seems to work.

Once fish die, the parasites drop off and/or die/rot themselves. I've been told you must have a live fish to do a skin or gill scraping. I've never done one myself but I sure wish there were a koi club or vet around here (none in my entire state!) so someone could teach me. Testing for the parasites in dead fish or in sediments would be a very iffy thing. It's better to test the live fish.

There are many kinds of fish parasites. Some can survive free living in the water for a few weeks, others can't survive more than a day. Some species or parasites can form cysts on the ground or the bottom of the pond while they wait for water or hosts to return.

Motoman, you got it backwards.

$450 for plants, and you're concerned about the expense and effort to care for fish, because you only paid $15. One of these days you'll see it the other way around. It's a sickness, fishy lover syndrome. And if you take care of them; in a few years you'll have bragging rights because they'll be worth more than your plants.

Do what you need to for your fish, they'll appreciate you for it. :D