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FAQs on Koi, Nishikigoi

Related Articles: Nishikigoi, Koi Varieties, Koi Selection

Related FAQs: Koi Varieties,

A couple of female Kohaku, one Sandan, the other Yondan.

Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
Volume 1. Design & Construction
Volume 2. Maintenance, Stocking, Examples

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by Robert (Bob) Fenner

Koi help for newbie lady     9/15/15
Good morning,
<Good morrow to you>
I have three koi in a 150 gallon pond in my backyard.
<Yikes; will start w/ a cautionary statement re this size/volume and keeping koi/Nishikigoi... Not easily done. Hard to keep small bits of water outdoors optimized and stable... chemistry, temp. wise... hard on such (ultimately) large fish
>
I noticed one of my koi had something wrong near her gill so I brought her in to my 60 gallon tank to view. She has what appears to be part of her flesh near her gill missing. The attached picture was taken last night and as you can see it is a "round" spot and as of this morning it is now elongated in appearance.
She is eating, shows no sign of stress and my ammonia levels have been running zero. I brought my other 2 in as well to view and they do not have any injuries, as a matter of fact all have doubled in size in 7 weeks! Any ideas on what this "spot" could be?
<My first guess is on mechanical injury... either the fish dashing itself against something or a predator whacking it.
Am leaning toward discounting environmental cause here... as the other fish are listed as fine. I would ask that you peruse the pond subsection of WWM: http://wetwebmedia.com/PondSubWebIndex/Pond%20Sub%20Web.htm
re pond design, maintenance (water quality), predator control... disease diagnosis>
I'm new to the hobby and would appreciate any feedback.
Thank you,
Sheila
<Much to know; actionable knowledge needed... but not knowing you better, best to lead you at this juncture to educate yourself. Do write back w/ more specifics as time goes by. Bob Fenner>


Note the sore on the gill operculum, missing scales, fungus on the tail

Scaredy cat Koi      7/15/15
Dear Crew.
I have two Koi in an indoor 55 gallon tank,
<Will need, or may require more room right now>

they have been in this tank for almost two years now and they are doing great and thriving and growing. But they still scatter and panic when someone walks into the kitchen where the tank is kept, hitting the rocks and glass walls of the tank beating their beautiful heads off, but no injuries yet ; )
<Uh, yes there are>

Any advise would be grateful...
Thank you!
Mr. John C. Hanna
<A much larger system or a move to a sizable pond.
Bob Fenner>
RE: Scaredy cat Koi      7/15/15

Well thank you for not answering my question! I live on a river and have a Great Blue Hereon problem they ate all the Shubunkin fish but left the Koi
<Ah yes; Herons can be very hard to guard against>
so I brought them in I love my fish and was devastated at the loss and did not want to leave the others to the same fate...
<Mmm, perhaps reading on WWM ahead of writing; as we direct folks... There are anti-depredation techniques to consider>
You know you all had several rules on sending in an e-mail I know that there are people out there that do that kind of stuff,
<?>
I do not feel that the "between the lines comments" are necessary. And if I where your Supervisor you would be fired!
<We have no supervisors, and are all volunteers. Perhaps my pond books (see Amazon) are more your speed>
Once again thank you for your courteous answer.
John C. Hanna
Customer Service Supervisor
Mr. Suds Inc.
<Read John; don't hate. BobF>

2 5 inch Koi; overwintering in/outdoors      11/20/13
HI
I was wondering if you could answer a few questions about my 2 approximately five inch Koi I have. (don't know their actual size sorry)
<No worries; this approximation will suffice>
we have been keeping them in an above ground stock tank (approximately 500 gallon) for the summer.
we are unable to keep the tank heated over the winter and I am afraid they will die if left outside in this stock tank.
would they live? or should I move them inside?
<Mmm, depends on how well insulated (thermally) the 500 gal. system is...
IF not too much vacillation in temperature (a few to several F. per any given day), they should be fine>
if I have to move them in Im afraid I don't have a big enough tank for them.
what would my options be on housing them indoors for the winter only?
<Tanks... kiddie pool... both covered, w/ tops>
I have a couple 35 gallon tanks, would that be big enough for the winter if I split them up? should I split them up?
<Unless there's the variation mentioned, or outright freezing; I'd leave where they are>
any advise would be greatly appreciated.
thanks
Jessica
<Welcome. Bob Fenner>

Re: Indoor housing Koi    7/20/12
Thank you for the insight and the helpful information. We have found the new house, and it actually has a water fountain at the side yard. It is a courtyard that sees little disturbance and is well-sheltered from both the elements and from most of the outstanding predators, though I don't doubt a starving coyote or neighborhood wandering cat could jump the fence. The fountain is not currently in use, and, if possible, I was thinking of converting it into a small pond, with only a fraction of the Koi, and house the remaining Koi with my friend, who is willing to take on overflow. There are many issues, of course, with this, not knowing the full history of the fountain, the fact that it is or was chlorinated before the previous owners left, and the issue of materials.
The chlorine pump, if there is one, will be turned off or disconnected entirely, the water swapped out and replaced after a good rubdown with bleach, if necessary, but for the most part, a good scrub should do fine.
It is full of algae, which may even have grown in the weeks since the fountain was turned off. The water available has a good parameter set, gH tested at about 160-180, and pH was solid between 7.0 and 7.5. So, since the water is about the same as the water at my current home, I expect the patterns of ebb and flow to be similar, with differences attributable to external influence.
The fountain itself is 42" x 64" x 14".
<Small>

From the absolute top of the fountain to the water surface, there is about 6" of free space, but when taking the height measurement, I excluded this space, so the actual water level was 14" from the bottom.. I calculated the volume, and found that filled to capacity, it would hold approximately 162 gallons. Therefore, I intend to purchase an external canister filter capable of operating for about 175 gallons, and will add some activated carbon harboring bacterial colonies from my existing filters to the filter media, if possible, will likely add a good amount of the water from my cycled tanks, and will perhaps purchase several feeder goldfish to create ammonia about a week after initial setup, then let the cycle run for about 3 weeks, keeping a close eye on the water parameters.
<Just use a bit of food. No fish>
 If the cycle is in adequate form by then, I will start adding my Koi.
However, the biggest obstacle I can see is the fountain itself.
The fountain is rectangular, and lined with ceramic tiles, and the bottom of the fountain seems to be concrete. My concern here, of course, is this material. The house, and the fountain, are not new. They have been there several years, which may or may not have  been enough time for either anything harmful to have long-since leeched out of the material, or for a sealing material to wear off and harmful chemicals start to leech into the water. The fountain has raised edges with ledges, and runoff does not breach the fountain. So, given all this, is there a liquid Master Test Kit that tests for lye and other such harmful chemicals that you could perhaps expect to leech from concrete?
<There is very likely VERY little of this at this time>
 Alternatively, is there a product I can use to easily and effectively seal the material to prevent the possibility of leeching?
Perhaps most importantly, can I effectively convert this fountain into a small pond with one or two Koi, or is this an ultimately hopeless venture?
If this is just impossible, then I will simply turn over the Koi to the friend of mine with a well-established Koi pond, and instead opt for a somewhat larger than "desktop" aquarium for my crayfish. Thank you.
<... best for you to keep planning on building a real pond in future. BobF>
December 21, 2011 1:15 PM
To: Crew@WetWebMedia.com
Subject: Indoor housing Koi

Before I begin, I would like to tell you that the arrangement is only temporary, and I am very well aware that Koi cannot be expected to permanently thrive in an indoor aquarium. However, for the time being, the Koi are small and immature enough that the current conditions in which they are being kept are sufficient. They receive a highly varied diet of Koi pond sticks, freeze-dried foods, the occasional live food, frozen food, and some fruits and veggies. They greet fruits and veggies I attempt to introduce with tentative caution, but if left alone for a while, eventually come to understand that they are food.
<Mmm, a good grade of pellets alone is fine>
They are currently housed in a 40 gallon tank with a filter that was made for a 75 gallon tank, in an attempt to assure adequate filtration during their stay. There are six Koi, most between 1-3" and one at least 4".
However, they show no signs of stress or agitation, and even get along with my dog when she presses her nose against the glass.
Now then, then only reason I opted to keep the fish indoors is because I live in an area where there is a nature reserve pretty much in my backyard.
Coyotes and red-tails are a constant, and the coyotes have even learned to imitate dogs barking to lure out pets. I have yet to see a raccoon in the neighborhood, but I am sure they are here.
<Raccoons are tremendous Pondfish eaters; very hard to keep out>
The soil quality of the area is extremely dense, with about 2-3" of topsoil, over a good 6" of clay. There are also very few pond building specialists with the capacity to help me design a pond with the depth and form necessary to keep these predators away.
<I will help you from afar if you'd like>
We may also move within a year. I perform frequent water changes on the tank, usually massive, and done slowly and with minimal invasiveness to minimize the stress to the fish.
<Do these weekly>
The water is cloudy, but it is a problem with the food I've been feeding them rapidly dissolving into the water, and by doing the more massive water changes, I am able to rapidly fix it. I plan to switch them over to Hikari Growth Saki, if I can get my hands on it, or the readily available steeple diets from Hikari.
<Both are excellent, as is the Spectrum pellet line>
The water I fill the tank from is hard with a solid pH of about 7.4 to 8, and the water is salted appropriately.
<No salt adding necessary or suggested>
I live is Southern California. Specifically, I live in Stevenson Ranch, CA. Is there anyone, or any place that I can turn to nearby that will help me to plan out an adequate pond or environment for my Koi?
<Here... as in WWM, and myself>
I myself am on a but of a budget, but am willing to devote any resource necessary to maintain the health and safety of my fish. A neighbor of mine has a pond, although it is not professionally constructed and vulnerable to predators, where, if the need were absolute, they have offered to temporarily house my Koi, should they outgrow the tank before an adequate pond could be constructed, or should we move. Any help, and an approximate estimate of how long it may take the fish to outgrow their current home is welcome.
<Likely w/in a year... I would be very skimpy re feeding>
The fish are not mature, and I am not even able to determine their genders, but they are healthy and active, and two have even become my wonderful provocateur fish.
<Ah good. Do take your time, peruse the Pond Subweb here:
http://www.wetwebmedia.com/PondSubWebIndex/Pond%20Sub%20Web.htm
From the top down. Cheers, Bob Fenner>

Pics from 15th Singapore Koi Club Show     6/11/11
> Bob
> Some pics from the Koi Show held this afternoon
> Perry
<Thanks Per. B>

       

Showa Sanke...        A little sumi bleeding on this otherwise gorgeous Taisho Sanke

Grand Champion             and Grand Champion Runner-up

Grand Champion -Non Gosanke     6/11/11
> Non Gosanke- are these the metallic category?
<Mmm, no; or not only... The Gosanke category consist of the Kohaku, Sanke and Showa types, these are almost always the Grand Champion and Runner-up (first and second overall winners)... the creation/use of non- or not Gosanke is used to allow/grant a winning status to non-traditional varieties (red/white and mixes of red/black and white). BobF>

1st Runner Up   ' 6/11/11
The club flew in judges from Japan
<A beauty... and as well they should. This removes much chance and discussion of favoritism, adds other aspects of legitimacy to the contest, and presents opportunities for learning. B

Now, stainless trough for Koi  10/25/08
I submitted a question yesterday regarding the safety of steel horse troughs as a pond. The response I received stated that the tank would be Ok for turtles. Would it be safe for Koi as well? Thank you so much for your time in answering my questions! What a wonderful forum you offer.
<Mmm, safe chemically, though I don't encourage this use. Nishikigoi appreciate much more stable circumstances (temperature et al.) than such a device can provide. Bob Fenner>

Turtles and koi mixed -- 07/18/07 Hello, Crew, I have a few questions. Will a 5-year old female Eastern Painted turtle eat koi that are larger than her? And will she leave an unfenced pond? What about a 3-year old male? Thanks, Joe <Hello Joe! Chrysemys picta picta is one of the nicest North American freshwater turtles (what we call "terrapins" in England, bizarrely enough after a Native American name for these animals apparently not used by most North Americans!). In fact, this was the second species I ever kept, and good fun it was too. Lived for many years before being passed on to a zoo when I went to college. Anyway, in common with other species in the genus, these animals are primarily herbivorous, which is why their optimal diet in captivity is one based on green foods. Juveniles will eat small fish as well as insect larvae, but the adults are too slow and clumsy to catch fish, though they certainly eat carrion. The problem is that in a pond the odds are biased towards the turtle because it is more difficult for the fish to swim away to safety. Feral red-ear terrapins have been reported eating ducklings in London ponds, apparently being released into the ponds by irresponsible owners bored with these large and somewhat difficult pets. So while you might be lucky mixing koi and turtles, and it's certainly be done, there are no guarantees at all. As for your turtles upping-sticks and moving out: yes, very likely. Even if they don't get out, there's nothing to stop predators like mink or cats getting in, so this is something to consider carefully. Cheers, Neale>

My koi   4/30/07 I have a larger pond about 2500 gal. and have 15 koi, I have noticed that one of them is pregnate <?...> should I separate it or just leave it alone, it would be hard to find the eggs after the fact. <Please read here: http://www.wetwebmedia.com/PondSubWebIndex/pdfshbreeding.htm and the linked files above. BobF>

Koi teeth? Sound production in Cyprinus    02/17/07 Hello Crew, <Hi there> My subject line is tongue-in-cheek but it's related to a question about Koi anatomy.  I have a few Koi I am 'growing' in my 45 gal tank over the  Winter.   I feed them Hikari Gold Medium pellets.  I noticed that the  larger Koi (about 7") produce an audible metallic clinking sound after they  consume one or more pellets. <Interesting> Do you know how this sound is being produced? It sounds as if the pellets   are being crushed somehow. Thanks for your thoughts <Mmm, Koi and all other minnows lack teeth on their jaws... Masticate in other ways... and though other fishes make sounds through snapping body parts (pectoral girdles, jaw areas...) and use their gas bladders as resonators... I don't know how Cyprinus carpio does it. Thanks for the report. Bob Fenner> Re: Koi teeth? Sound production in Cyprinus    - 02/17/2007 Bob, <Yo!> I think I just figured it out.  The sound is only emitted after  the second or third pellet ingested.  I believe it is simply the pellets  themselves rubbing against each other as they are peristaltically squeezed down  the 'ole gullet! <Ahh! I also considered whether the triturating action of the "pharyngeal teeth" and the hard pellets were at work here. Thank you for this follow-up. BobF>

Mixed Koi and Goldfish... chasing beh.   7/31/06 I have a pond with 9 koi and 7 comet/Sarasa/Shubunkin.  The large Shubunkin chases all the fish with it's head at the others anal fin. Is this fish being territorial, trying to mate, or just being an aggressor? <Mostly the middle, but likely a bit of the others as well> We are not sure if we should remove it from the pond or if this is normal behavior. What is your advice? <Moving the aggressor if apparent damage is being done. Might be able to be re-joined when the weather starts cooling down... Bob Fenner>

Market Size for Koi 12/2/05 Hi there!! <<Greetings!>> I'm from South Africa, currently doing market research for Koi. Could anyone PLEASE give me any estimate for the market size for Koi? Kind regards, Ane <<Well, as they are colored and/or coloring up, best salable, usually at around 3"-4" (7.5cm - 10.5cm)) in total length, though I have seen them offered as small as 2". I've not seen koi actually ON the market at smaller sizes, but have been involved in a small breeding/rearing operation. Marina>> 
Market Size for Koi - II  12/5/05
Hi there! <<Hello again, Ane.>> Thank you for replying.  <<You're very welcome.>> What I meant, was the production/industry size for Koi. Kind regards Ane <<Did my previous reply give you the answer you sought? The question just seems to be re-phrased, ultimately meaning the same thing as I understand you - at what size can koi be "market-ready" or "salable", yes? Marina>> <Most small koi are sold at more than three inches total length... four is most common and easiest to ship with low mortality, generally sold in two inch increasing increments beyond that. RMF>

Butterfly koi care 11/3/05 Can you send me some information on the care of "Butterfly Koi"? Thank you <Mmm, same as non-butterfly koi... same species (Cyprinus carpio)... our coverage here: http://www.wetwebmedia.com/PondSubWebIndex/Pond%20Sub%20Web.htm  Cheers, Bob Fenner>

I just bought koi help!!! dear sir/madam     I am writing to you in regard to my koi. I am a Kuwaiti boy who bought (rescued) 2 koi fish from the Friday souk (like a flea market but with animals and in very bad condition of care and cleanliness. Anyway, so the koi are about 7 inches long and I would like to know which sex they are and when they breed. <Please read here: http://www.wetwebmedia.com/PondSubWebIndex/pdfshbreeding.htm> one of them is stubby with a chubby abdomen, and the other is thin and has a long tail which I have never seen before in koi. so can you please help me.     Yours faithfully Abdulmohsen Al-Reesh <Please read on WWM re Koi Systems, Health... Bob Fenner>

New small Koi acting... lethargic Hi, <Howdy> My name is Billy, I have a question about Koi. I recently rec'd a delivery of 50 small(2") Koi. <Small... especially for moving about in the cooler months of the year...> The fish have good color and don't seem to have any illness as far as I can tell. But my concern is the fish lie on the bottom of the holding tanks either on their belly or on their sides some even tend to roll over upside down. This almost sent me into shock when I got up this morning and peeked into the holding tanks (4 of them) and saw only 2 fish swimming around.  After getting the net to scoop out my last paycheck and flush it the fish scurried away out of the net so I decided this may not be a total loss quickly I did a 50% water change and about a hour later the same thing. the fish do eat well and liven up at feeding time. So my question is do baby Koi normally act this way or did I end up with a box full of slowly dying fish? Any advice would be appreciated. <Good descriptions... and I do hope your fish are just "jet-lagged"... this is likely the most reasonable explanation... and they should "come around" within a few days... in the meanwhile do be careful not to overfeed... and keep an eye on ammonia concentration in their water. Where they were from water-wise is highly likely different than your conditions... but with time they should adjust. Bob Fenner>

Indoor Koi 7/9/03 Hello, I was wondering - can Koi be kept in aquariums? Thank you, Emily <they certainly can, my friend... but they do require very large aquaria even within a short period of time. They can grow to be well over 24" in just a few years and require very good husbandry (frequent water changes and attention to water quality) and heavy filtration. Do read more about Koi in the archives at wetwebmedia.com Best regards, Anthony>

Golden Orfe Changing Color Hi my golden orfes have got some black shadowy marks appearing on their bodies is this natural coloring as they get older (they are 4years old) or is it a disease that needs some attention? <Most likely nothing to worry about. These and many other species do tend to change colors a bit. Watch them for any symptoms of illness but I wouldn't worry too much. Ronni>

Re: optimizing growth in Koi Hi Anthony, <cheers, Kelly> Thanks for the info.  As far as water changes, I think large weekly ones would be preferable to setting up a 200-300 gallon daily auto system...since I'd have to DeChlor that water anyway. <very fine... better than having reservoirs> I don't mind changing 30% twice weekly, as I did during the break in period.  I'm setting up an extra chamber where this water can be easily mixed with DeChlor before remixing with pond water.  So that way I can be changing more than 50 % each week during heavy feeding season. <that will be outstanding and a primary vehicle to dilute growth inhibiting elements> It sounds like you are recommending that as the main way to reduce growth inhibiting factors?   <agreed> But is it still recommended to use carbon, protein skimmer, and ozone?   <all yes except skimmer. Skimmer only if your system is without plants and does contain some salt. Skimmers need at least slightly salted water... common with Koi.. can be suspended during breeding or not> If so, can you recommend where I can look for ozone equipment to buy?   <many fine places on the internet. I haven't shopped recently to know who might have the best price/service. Do some keyword searched for aquaculture supply houses. They will have less expensive and likely heavier duty models than those marketed for pond enthusiasts> Also, can I use just a protein skimmer without ozone?   <you can... but it will not work as well> I use them indoors on my marine tanks, but somehow I had the idea that they were never used on koi ponds. <good heavens! :) They are extremely common on ponds for their efficacy with high organic waters. Most good pond books make favorable mention of them. Do look into it and weigh your options> Thanks for your help, Kelly Evans <our pleasure. Best regards, Anthony>

Optimizing growth in koi and Ozone Hi Bob, I've been reading your very helpful articles at WetWebMedia about growth rates, how to optimize them, inhibiting factors and so on. I keep koi, and have been learning more about many of the things you discuss.  I just got back from my first trip to Japan, <congratulations... sounds wonderful> where I bought some fish first hand from the breeders themselves.  So I know about their bloodlines and growth potential.  And I also learned about growth inhibiting hormones. My question is, can I remove these hormones using a protein skimmer and/or activated carbon?   <not with certainty or consistency although both methods are recommended. Ozone and water changes (daily/frequent are best for maw grow out like slow flow through) My pond is about 6000 gallons, and I have about 25 koi, 10 being 22-24", the rest smaller. <we could automate the system to do daily200-300 gallon water changes... or weekly larger ones. Quite easy to supplement your monthly maintenance. Koi farmers to massive daily water changes for optimal growth>   Also, I read about the use of ozone to reduce growth inhibiting hormones, but so far, it sounds dangerous and expensive to me.  Is this so?   <heavens no! It is dangerous if misapplied like iodine, medications and many other things. But there is no magic involved. Ozone is remarkably simple and easy to use. A RedOx controller offer metering and redundant control of dosing, simple activated carbon on air and water effluents mops up the residuals. The best public aquaria and fish farmers all use it> Could ozone kill the beneficial bacteria of the system, or otherwise hurt the fish? <impossible to do either if it is not allowed into the system (bypassing carbon). Nitrifying bacteria are benthic and not free-floating. They would never get into the reaction chamber to any significant degree. Fishes can't swim into the reaction chamber either <G> so... simply control the effluent with carbon (mandatory and standard with ozone)> Any suggestions would be appreciated, <OK... bet on the Pittsburgh Steelers... they are going to the Superbowl!> Thanks, Kelly Evans <best regards, Anthony Calfo>

Koi/ goldfish Hello, Please tell me if it is true that koi have whiskers and goldfish do not. <Actually, both these minnow species bear barbels at the corners of their mouths... more prominent in Koi/Carp (Cyprinus carpio) perhaps, and much more noticeable with age, size...> we have many babies from a pond of koi and goldfish and I am trying to tell them apart. They are now about 3 inches long. Thanks Pat <Mmm, not to add to the question, but there's even a chance with both species present that you have a cross (called Orfes) between these two... Are the young pretty streamlined? Grew quite quickly (the last couple of months?). If so, chances are these are Carp. Bob Fenner>
Re: koi/ goldfish
<< Are the young pretty streamlined? Grew quite quickly (the last couple of >> Some yes, some no...so chances are we have both and maybe some Orfes as well. I was just trying to separate them and decide who to eliminate. Our pond is about 16 ft x 16 ft. We have around 30 young fish in a tank right now. Thanks for the info <You're welcome... maybe some of the neighbor children would appreciate the excess... Bob Fenner, looking for future aquarist recruits>
Re: koi/ goldfish
<< maybe some of the neighbor children >> Gave a few away...seems the moms like them to enjoy our pond and 3 tanks:) If I can separate the Golds from the koi. I may be able to sell them to a shop <Ahh! An entrepreneur as well! Bob Fenner>

Koi Fish Dear Robert {Bob}, I have a very big fish that seems to be a Koi maybe. I have been looking for them, and have not found any, on the internet, someone's pond, or any websites. So I was wondering if you could help find just what kind of Koi it is. It looks just like a Koi but as gold and pretty as a giant gold fish, same body structure and shape, but gold; not yellow. What kind of fish is it? <Many possibilities from this description... Please take a look here: http://wetwebmedia.com/PondSubWebIndex/koivarieties.htm Is this what you have? Do you have images you can share? Bob Fenner>

RE: Distinguishing koi from any other gold fish Not really, I think my question wasn't phrased properly. How can I tell a koi apart from a gold fish.  <Oh... the two species are easy to make out when side to side... the Carp are much more "broad-shouldered"... wider at the head by far, larger eyes, scales... than the variety of Goldfish called a Comet... other sport mutations of Goldfish, like Orandas, Fantails, Bubble-Eyes... are much easier still to distinguish. Please see here: http://www.wetwebmedia.com/PondSubWebIndex/koivarieties.htm re Koi Varieties... and in places on WetWebMedia.com re different shapes/sizes of Goldfish> From your answer, perhaps I should have also asked "when is a koi not a koi?" You mentioned golden Orfe. I have seen these on sale but they look a totally different fish - much slimmer. Do you suggest I get rid of my large ?ghost koi? <Not at all... I would keep what you have... it's a common practice in Japan (and elsewhere) to have such a brown or black individual (for good luck) in ponds. They lack "teeth" on their jaws... will not eat each other though quite different in size. Bob Fenner>

Koi with Opaque White Eye I'm trying not to panic... <Won't help, unless it stirs you into action> I have a 1000 gallon pond with external filtration lots of plants. None of the koi have been in the pond more than 2 months. PH is 8.4 water hardness is o.k. no nitrites, no ammonia. <pH is a bit high... if through regular activity you can maintain this closer to neutral (7.0), this would help with fish health, keeping the pond more algae-free... Much to say here re pH manipulation...> I found a koi floating dead yesterday. I found no injuries but there was a bit of brown slime near his gills on one side of his body. I thought it might be because it probably was floating there most of the day until I got home. Today I noticed the largest, best eater in the pond had something odd about one of his eyes. I netted him and took a look. <Oh...> His eye seems to be glassed over...opaque and the pupil, while visible is tiny. The other eye seems to be alright. The other fish haven't shown any signs of trouble yet though they have been congregating in a corner for very long periods of time. There are a total of five koi in the pond right now. Thanks for any help you can offer.  Alan <All could be coincidental... the one fish dead as you state just not being discovered, the one with the glassy eye just having suffered a mechanical injury... Nonetheless I would execute a water change, vacuum the bottom of the system, and ready whatever you have as a treatment container. Please read over the "Koi Health" area here: http://www.wetwebmedia.com/PondSubWebIndex/pdfshdisart.htm  and the surrounding, linked files. Bob Fenner>

Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
Volume 1. Design & Construction
Volume 2. Maintenance, Stocking, Examples

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V. 2 Print and eBook on Amazon
 

by Robert (Bob) Fenner
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