The Most Effective Tips for Koi Pond Maintenance

koi pond water testing

Koi Pond Water Testing

Having a Koi pond at your home is undoubtedly the quickest way to reduce stress and anxiety that you have to deal with on a regular basis. This peaceful and quiet place is essentially a man-made paradise. Apart from eliminating stress and tension of your mind, a Koi pond is a perfect way of adding beauty to your backyard or any outdoor space.  However, it requires some effort to keep it in its healthiest and most attractive condition. You may have heard that building a Koi pond is a much easier task as compared to maintaining it. However, if you take proper care of your Koi pond right from the beginning, you can avoid many complications later on. With that in mind, let’s take a look at some of the most simple and effective precautionary steps that you can employ to keep your Koi pond in the healthiest state.

Perform constant water checks to avoid common problems

Normally, Koi pond owners experience problems like water leakage or seepage from their ponds. There can be many instances where natural evaporation also negatively affects the quality of water. Moreover, many Koi pond owners have to deal with other serious problems like acid rains and excessive fish waste.  In order to avoid these common but serious issues, it is highly advisable to perform constant water checks. Although it’s true that Koi fish can be easily taken care of, poor water quality can cause even the hardiest fish to suffer from health issues.

Maintain the right temperature

People living in colder regions shouldn’t worry, they will be happy to know that Koi can survive during the months of winter. When ice deposits on the surface of water, these fish can essentially hibernate under the surface. In order to be on the safer side you should use a water heating system to maintain the perfect temperature for Koi growth.


Avoid overfeeding

Over feeding your Koi fish is one of the unhealthiest practices and should be avoided at all costs. However, when feeding you should take that opportunity to evaluate your Koi fish closely. This will help you to detect any diseases or injuries that have occurred to the fish. Overfeeding can lead to poor water quality which itself can initiate a host of  additional problems down the road.  These problems include high ammonia and nitrites in the water to fin rot on your fish. 


Properly maintain all your Koi pond supplies

These supplies normally include a good quality filtration system, a powerful pump, protein skimmer, a water heating system and ultraviolet sterilizer. For instance, the water pump is used for pumping water in and out of the pond which is essential for maintaining proper aeration in the pond.


The filtration system in combination with the protein skimmer is very useful in keeping the water clean and healthy for your Koi. As mentioned previously, a water heating system is useful in maintaining the right temperature in the pond during the colder months.


There is no doubt that Koi fish are one of the most graceful and attractive fish to keep. Another interesting thing about Koi is that they also have an fairly decent life span (you can expect 15-20 years and in some cases much longer). However, if you don’t take proper care of them, they won’t be able to live to their potential.

For a more comprehensive coverage of koi maintenance click here.

67 Responses to The Most Effective Tips for Koi Pond Maintenance

  1. Mary says:

    We have a backyard Koi pond that we installed several years ago and have had no problems until this last month or so,now our fish are at the edge of the pond where the water fall flows and seem to be having problems getting air.We do have about 50 midium size fry now for the first time,they appeared late last summer and wintered over well,we have 7 large size Koi.
    We don’t know what to do.

    • Koi-Care staff says:

      Okay, so it sounds like you have a low DO problem (dissolved oxygen). Koi DO requirements are around 6 mg/l so there could be a few things going on. You could be experiencing excessive nutrient loads in the water which would cause increased growth of algae which in the short term creates more DO but once that algae dies it decays and that decaying process depletes oxygen which may describe your situation. You may have had a really hot summer and warmer water holds less DO than cooler water or you may have an increased oxygen requirement in your pond by having the fry in there and your aeration systems are inadequate to meet the increased demand. In short I would check DO levels as well as phosphorus and nitrate levels. If need be you may have to install more aeration equipment to increase DO.
      Thanks for stopping by.

  2. Jennifer Nelson says:

    We just bought a house that we knew had a water feature, but I discovered yesterday that there are koi in the small pond part of the water feature. The house had been vacant for over a year until we moved in last week. Will it shock the fish if we start trying to clean up the pond, or I guess the question would be, where do we start in trying to care for these fish? We are so excited about them, and want them to be happy and healthy!

    • Koi-Care staff says:

      Congratulations -that’s always nice when you get an added bonus when buying property. Well, if they haven’t been tended to for a year then SOMEthing is going right! I don’t know what kind of systems are already in place at the pond such as filtration or aeration but I would suggest starting with a basic water testing kit -it won’t be complicated to make sure your water remains in the correct balance. I would almost be tempted to suggest not doing much to the pond if you already have content and thriving koi. You may want to do some supplemental feeding with koi chow though. If you decide to really ramp it up and want more koi or a bigger pond I offer a pretty comprehensive koi manual on my site that covers everything you’ll need to know.
      Good luck and congratulations!

      • Jennifer Nelson says:

        Thank you so much! I did buy some koi food, which they seem to really enjoy – especially the big one, who pushes away the little ones to get the pellets! I found a manual for a uv filter, and there is filter cleaning solution in the laundry room. There is a small waterfall that we hope to get up and running within the next two weeks while my husband is home on a short break from being on the road. Here is my next item – there is some other kind of creature living with the koi, and I’m hoping you can help me figure out what it is… It is black, with eyes on top of its head, and he comes to the surface every once in a while and puts his eyes above the water. He is very skittish, so I don’t get a very good look at him before he disappears. I was thinking mudskipper until I learned they like salty water. Now I’m thinking some kind of frog, I guess, but I don’t know if frogs can stay underwater as long as this guy does. Any thoughts? :) Thanks for your help with the koi – I am definitely going to get a pH kit, but I will try not to upset what they already have going on in the pond, since it does seem to be working, like you said. Take care!

        • Leslie says:

          How strange, I am in almost exactly the same situation as you! We also bought a house (in February) with a little pond with 17 fish (I think they are goldfish, not koi). This pond also had not been maintained – but not for just a year, for the entire time it has been there. The previous owner straight-up said he did nothing to maintain it. There is about a foot of sludge/pine needles/leaves/sticks/pine cones in the bottom. There was a LOT more (water was so dirty we literally couldn’t see the bottom). We are gradually hacking away at it but every time we go at it with nets, it throws up a lot of silt into the water. We’ve been using a pump/filter, good bacteria capsules on the filter, and some good anti-sludge bacteria stuff so we can at least see the bottom now. I’ve seen some kind of stuff you can put in the water that’s supposed to clear it up, but I am worried about adding too much stuff to the pond for the same reason Koi-Care said; it managed to survive somehow and I might throw off whatever balance is there. BUT it was FILTHY and I’m sure in general not good for the fish. Plus, we have tried feeding them, but they completely ignore any food and I see them stick their heads in the sludgey stuff and wriggle around, so I think they are managing to eat out of it. We lost 1/3 of the fish recently (I think the pest control sprayed our nets) and have added three koi just this past weekend. After three days they are still swimming around and getting along with the other fish. So sorry, I just wanted to share, guess I don’t really have a question. :)

  3. Dwain says:

    Koi pond we adopted last season is mature with Koi having grown very large( 4 of the 7 over 18″ long)…I noticed lately they do not come to the top for food anymore but when I walk back out to the pond later food is gone. They used to watch me come up to pond and then aggressively feed on food. Now they tend to stay swimming lower in pond and ignoring my feeding so that is a concern in that they have changed their behavior thus so……any thing come to mind as for the cause in behavior towards feeding?

    • Koi-Care staff says:

      My best guess would be that they are associating your presence with perhaps the presence of something else like raccoons or wading birds that may be attempting to prey on your koi. You may also have some neighborhood kids hanging out at your pond throwing rocks at the fish (though I don’t know if you have neighbors or what the layout of your property is). Hope this helps

  4. Glenys chen says:

    We have a 2600 gallon pond and have 12 XXlarge Koi in the pond. Is that too many? Ans will they survive. We also have a 2000 gallon bubbler going on, so hoped that helps. Can we put more fish in? Each of the fish is nearly 30″ long. Thank you my pond is only 3 1/2 ft deep. Will they do well in winter.?

    • Koi-Care staff says:

      I would give it some time and be sure to check the water quality -a
      lot of metabolic activity via the fish can change nitrate and nitrite
      levels. I don’t know that I would go much beyond that number of fish
      though. In my experience, fish that aren’t crowded do much better.
      As far as winter goes they should be fine, koi/carp are adapted to
      over-winter without a problem. your depth seems fine to me. Try not
      to over feed as that can create problems with excessive nutrients in
      the water. Submerged plants are always nice too for a place to
      shelter up for koi and get shade in the summer as well as provide
      dissolved oxygen in the water.

  5. Carol Bell says:

    This Spring, we bought a house with a Coy Pond and Waterfall
    in the backyard. After moving into the house, we had a
    professional pondman come and clean our pond. We also had to
    purchase a new circulating pump. The water had previously
    been extremely cloudy. After the cleaning the water stayed
    clear (could see to the bottom) for about a week. Then it
    began to get mucky again. The pondman suggested that we buy
    some more water lilies to keep it clean. We did that, but it
    did not seem to help much. Now the water is very mucky again.
    We cannot see the fish except when they come up to eat. And
    the top of the water has a scummy film. What do we do???
    We have about 7 gold fish, some kind of medium size white
    fish (1), and 1 large white catfish.

    • Koi-Care staff says:

      so it sounds like your fish are actually doing okay. My guess is that
      even after getting your pond cleaned out that you still have a great
      deal of unconsolidated muck in your pond that is getting disturbed and
      gettting mixed into the water column. Another possibility is that the
      cleaning triggered an algal bloom perhaps and that is clouding up the
      water. It may just be a matter of time before that bloom dies and
      your water clarity is regained. If your pond cleaning guy really did
      clean out all the muck then there should be no way that there is any
      more muck to be suspended unless 1) there is more muck in the pond
      that he failed to clean out or 2) something else is clouding your
      water like algae. He is right though, plants are always a good thing
      to have in your pond because they process nutrients in your pond and
      if they are the type that root down then they are helping to stabilize
      the mud/muck where they are rooted.

  6. Jean Theron says:

    Hi There, i have a Koi pond at my shop but everyday i have to remove the algy from the sides. Its collecting everyday. what would be the causes of this happening everyday and is it safe for the Koi
    Thank you

    • Koi-Care staff says:

      Hi, algae won’t grow well without sunlight and nutrients. You may have excess nutrients from your koi pond in the form of uneaten food or nitrogen-based koi waste. There are certain snails you can get to ad to your pond to deal with the algae growth or get a powerful filter to deal with the excess nitrogenous waste.

  7. Dr Gajanan says:

    Hi There i Have biught fish tank silver koi. Most of times my koi sits and turns on side at the base of tank . What might be the cause?

    • Koi-Care staff says:

      Hi, its sounds like one of two things is going on. Your koi either has some sort of parasitic infection or you have high ammonia from lack of or lacking filtration. I would suggest checking closely to look for visible external parasites as well as testing your water chemistry.

  8. RIDHAA says:

    I have a pond in my yard , i have only recently started paying attention to it since we bought the house ,

    i filled the pond with water and added a dechlorinating liquid to the water .
    after about 2 weeks the water level has dropped tremendously .
    it would be quite expensive to keep addin water and my chlorine levels would be high .

    what could be the cause of this ? and what can i do to save water in ther pond ?

    • Koi-Care staff says:

      So I gather you are losing water not just from evaporation but seepage into the ground? Sounds like you may need to install a liner at the bottom of you pond. I don’t know how big your pond is but a liner would stop seepage loss. In terms of chlorinated water from your residential water source there may be in-line chlorine filters that you can install that would effectively deal with the chlorine before the water enters your pond.

  9. john orly says:

    i have a pond in our garden, can i ask when is the time to change the water as it gets dirty? can i change it’s water about 1time a week?

    • Koi-Care staff says:

      Yes you can certainly change water out once a week but I would do something like a 25% change. I’m not sure how big your pond is but of course its always easier to have an multi-faceted filter system.

  10. Joe says:

    I was wondering if you could help me?
    I would like to know when is the best time to open my Koi pond. I live in Louisville Ky. and the temps have been erratic, I usually open my pond around this time of year.
    I usually do a complete water change and clean the pond.
    I keep the pond pump off in the winter but the fish are out and swimming around the water temp. is around 50* .
    I normally put my fish in a small pond while I do the cleanup will this stress them out too much?

    • Koi-Care staff says:

      Its always a good idea to get out a lot of the muck and sludge etc. from your pond but I would recommend waiting a bit longer until the water is at least 55. When fish are coming out of a winter state they are largely running on fat reserves and their immunity to disease may be a bit reduced due to the lack of activity and regular feeding. Moving and handling the fish may cause some stress and that can cause fish with immune systems that aren’t “up to speed” to be more susceptible to disease (such as carp pox which is often associated with a drop in water temps in the fall and increasing temps in the spring). And if you wait until the water is 60 they will be that much more strong in vitality. Good luck!

  11. Paul Harold says:

    is “methylene blue” helps for a new home made fish pond, im a newbie in taking care of koi fish :)
    or what to do step by step?
    my pond is newly painted about 3 days ago..
    thank you so much

    • Koi-Care staff says:

      Methylene blue’s primary function in the world of fish husbandry is as an antifungal but also will act as an effective antibacterial agent. Hobbyist will use it to treat the protozoan that causes the common fish affliction, Ich. Its also a good substitute for malachite green as its less harsh. It actually has quite a few applications and not just in fish keeping. As for taking care of koi step by step, there’s more to that than I could write in this response but my advice to avoid a lot of potential problems is to 1) keep an eye on your water chemistry and 2) don’t overcrowd your koi pon (less is more)
      good luck, Koi-Care

  12. Joe says:

    Hi, We live in Michigan and this winter killed all of our fish and frogs in the pond. At smoepoint the aerator quit working but I think it would have frozen solid and killed the fish anyway to the terrible cold we had. It was a shame as some of the 15 fish were at least 10 years old and we enjoyed the chirping frogs in the springtime, there were 18 of them dead! We are going to take the opportunity to renew our pond and make it better. Question is what is the best way to clean while retaining the plant life and what equipment would you recommend to replace our already old pump, non0existent filter and a aerator or heater?Thanks for your help!

    • Koi-Care staff says:

      So to clean out the muck without damaging plant life can be as simple as removing the still potted aquatic plants at the bottom of your pond but it sounds like you have established plants so you may want to look into what’s appropriately called the “muck vac”. The vet site ( sells them for less than $100. I think this will be a good solution for you to remove much while not wrecking your established plants but you may want to look into potted plants that sit at the bottom of your pond that remain potted that you can easily remove during cleaning efforts. I have an article here ( about pond plant choices.
      For equipment look into the following:
      Little Giant makes a pump for average sized ponds. It will move around 1900 GPH and that model is called: 566409 WGP-65-PW
      EcoPlus for smaller ponds. This will move around 400 GPH 728310
      Patriot Koi Pond Pump is for larger ponds are will move around 8K GPH
      Tetra Pond has a nice filter called the “Bio-Active Pressure Filter” -I think they come in various sizes.
      Lifeguard Aquatics makes an filter system called the All-In-One Filter and its pretty popular.
      Look at Aquascape or Laguna for aeration.
      Again Laguna for heaters but K&H makes a really good 100 watt heater for koi ponds.
      If the filtration system you choose does not have UV consider an in-line UV. Laguna has an inline system called the Hagen Laguna UV that adds extra sterilizing power.

      Good Luck, Koi-Care

  13. Valarie F says:

    Hi I have always wanted to do a koi pond. Right now I have 2 very small Koi in a 30 gallon tank and taking care of them inside the house.
    I am reading this and find It very helpful and will be on here frequently. I live in North Carolina and the weather is humid in the summer and cold winters. We dont freeze or get too much snow where I’m at and when we do it melts quickly.
    Some questions I have:
    How big should the Koi be before putting them in a pond? Nevermind it says when they at mature leel juveniles should be in at least a 29gal tank. :)
    So how many inches is maturity? LOL
    How what dimension should the pond be?
    How do I acclimate them from my tank to outdoor pond?
    What plants will be beneficial to the pond?
    I am doing research and reading and learned quite a bit so far.

    • Koi-Care staff says:

      So how many inches is maturity?

      Maturity (at least sexual maturity) is really measured in time so around 2 to 3 years of age is considered “mature”

      How what dimension should the pond be?

      Pond can be whatever dimensions you would like it to be and what your landscape can handle. The size of your pond will dictate the number of fish you pond will have. You wouldn’t want a small pond with a ton of fish in it. You can get pre-fabricated plastic ponds that you just drop into the ground or you can do one in concrete -there’s lots of options.

      How do I acclimate them from my tank to outdoor pond?

      Temperature swings can affect your fish a lot so be sure to acclimate them slowly to any temperature changes. Also you could slowly introduce water from your established pond to your aquarium over days to get them acclimated to that water. I would make sure that the water in your pond you’re going to be building has enough time to establish itself chemically such that your media material has plenty of beneficial bacteria growing on it etc.

      What plants will be beneficial to the pond?

      In terms of plants see my article here:
      Good Luck, Koi-Care

  14. Golden7 says:

    I am a beginner level and have 3 kois plus 20 others fishes in a 50gals aquarium tank . Over populated ?Too many?? My desire was to keep the water clear as possible. But the water is really milky .Please help
    Thank you

    • Koi-Care staff says:

      that many fish in so few gallons -I would say you are experiencing some overcrowding. Each one of those fish is producing nitrogenous waste and it looks like your water clarity and quality is reflecting that. Fish, like people, don’t want to be cramped and though it seems like you may get more enjoyment out of having more fish you usually end up with more problems. In the case of having fish as pets “less is more”. You may also want to revisit the power of your filtration system too.
      Good luck, Koi-Care

  15. Janine says:


    I have gold fish and koi in one pond.

    I think my one gold fish has dropsy as it has just gotten so fat or bloated.

    will this affect my other fish and how can I fix it?

    also what is the best way to look after fish in a pond, as it is outside etc…

    and how often do I feed the fish as I was told when I took them over to feed once a week but I see 2-3 times per day?

    I love my fish and want too add more but just im worried as one has disappeared already.

    and I have a filter pump is this sufficient for them?

    many thanks


    • Koi-Care staff says:

      Janine, dropsy is an internal bacterial infection or kidney issue/infection and is actually difficult to treat effectively. Its not all that contagious but I would quarantine anyway and add some salt to the quarantine tank for some osmotic relief. Depending on the stage at which your fish is with dropsy you may need to do a series of antibacterial injections.
      So feeding rate of your fish is a loaded question because there are a lot of variables here. What is the season, water temperature, how big are they, how many are there, how much supplemental food is available (i.e. aquatic plants, insects etc.). When you feed floating koi chow you are able to see what is left over at the end of feeding time so you can better judge how much you need to reduce feeding or increase it if nothing is left over. Having leftover food is not going to negatively affect your water chemistry. You want to find that balance. For the most part your feeding rate is largely going to be dictated by water temps. as that is what will affect metabolism the most. I’ve attached a useful feeding guide that I found on -this guide sums it up as well as I could.
      You can add more fish if you want but I wouldn’t over-do it and make it too crowded. Your filter and pump should be sufficient assuming its rated for the size pond that its installed in. If you want to learn more about proper water chemistry, see my article on it here
      Good luck

  16. Karyl Holliday says:

    Hello, I have a koi pond that I’m really getting into. I had a Blue Heron take many of my fish, so now I have been paying extra attention and doing extra research. I have taken care of the bird problem (nonviolently lol) and I really want the new koi to thrive. I also have some commets that had babies last year. How do I best insure that my koi will breed?

    • Koi-Care staff says:

      Karyl, on my site there is a new article about koi breeding. Its called “I’ve got koi fry, now what”. If you still have questions after that let me know.

  17. Michael says:

    I have a pond which was quiet clear until I 12 Koi. then the water went increasingly green with what I suppose is algae. The pond gets very little sun as it is in our entrance atrium. I have tried all sorts of pond chemicals to help flocculate the water but to no avail

    Please can you help, we haven’t seen the poor fish for weeks now !!!

    • Koi-Care staff says:

      Green water which is essentially single celled algae is often associated with spring and summer as that is when ponds begin to experience increases in sunlight and water temps.- both important elements for algal growth. However, another element that aids in algal growth is nutrients such as nitrates. So right off the bat check your water chemistry and make sure you’re not feeding to excess which can result in higher nitrate levels. There are chemicals out there as you’ve discovered that will help to mitigate for green water and those include a products like AlgaeFix and Accu Clear. To really get at the heart of the problem though your water chemistry comes first and after that the next best approach is an in-line UV light as part of your filtration system. UV is a very effective control for algae and doesn’t involve chemicals that have the potential to complicate things.
      Hope this helps

  18. Tricia says:

    Hello! I could use some help.. I bought a house that has a fairly large koi pond with koi and gold fish in it.. it is atleast 3 feet deep with gunk. The previous owners couldnt maintain it so now im trying to.. how can I remove the gunk and the koi and clean it out without killing the koi?

    • Koi-Care staff says:

      So to clean out the muck without damaging plant life can be as simple as removing the still potted aquatic plants at the bottom of your pond but it sounds like you have established plants so you may want to look into what’s appropriately called the “muck vac”. The vet site ( sells them for less than $100. I think this will be a good solution for you to remove much while not wrecking your established plants but you may want to look into potted plants that sit at the bottom of your pond that remain potted that you can easily remove during cleaning efforts. I have an article here ( about pond plant choices.
      By the way, 4 feet is really a better depth for your pond if you can achieve it.
      good luck

  19. Joey ceselka says:

    Hey, I have a fairly large butterfly koi and 3 smaller koi I have a pond but I didn’t put them in it yet I currently have them in a 50 gallon tank, the big koi I had for about a year and it’s fine but the 3 that I just bout don’t swim that much they eat and they’ll swim a little but they mostly stay in one spot what should I do ?

    • Koi-Care staff says:

      Well 50 gallons isn’t that much space for 4 koi so that may be a factor in why they are not moving or you may have gotten koi with some health problems. I would put your big koi in when your pond is ready and then do the small ones one at a time so you can determine if changing their habitat affects their behavior. Have you taken steps to make sure that the 50 gallon tank has plenty of aeration and filtration? With four fish and a small space waste can build up quick and oxygen can get depleted.

  20. christal says:

    We have a 26000 gallon pool 30′ ×15′ and 3-6feet derp…. that we converted into a gold fish pond. I can’t seem to find large enough volumes of algefix type products to get the water clear any more than 1 foot deep…so lower 3-5 feet is totally green. Also having trouble finding a filter uv or carbon that can cycle at this high volume. Fish seem very happy…and reproduce like crazy. Direct sunlight and only small fountain for air circulation at this time. Will barley really help with the nutrients. What can I use to eat up the sludge…
    refer nstural over chemicals. Again finding products in volumes high enough for 26K gallons proves difficult.

    • Koi-Care staff says:

      Hi, I have a swimming pool that is 30 by 15 with a depth range of 3-5 feet and its about 14k gallons -if your pond was 30 x 15 x 6 all the way across it would be 2700 cubic feet or just over 20K gallons -I’m thinking that your pond is actually under 20K gallons. This is obviously important to be as close as possible to the actual volume for the purpose of adding chemicals etc.
      Not all algae is bad. For example, string algae is actually not that bad for your pond- the fish eat it and it produces oxygen. Of course it looks bad and will suck up oxygen when it dies and decays but other types of algae are normal to have in your pond and won’t cause problems. My guess is that this algae that is in the lower 3-5 feet is a carpet-like algae and is under 2 inches in length. You will want to keep that stuff around. Its typically 1/4 of an inch to 2 inches and under normal conditions will cover everything. As you have found out algecides won’t do too much to it -thats fine, it won’t hurt your pond to have that algae. It sounds like your pond it doing well and your fish are happy and that’s all you can ask for.

  21. Al Motta says:

    We’ve got an 80 gallon outdoor pond – an old molasses boiler.
    In it, we’ve had (5) 5″ goldfish and (1) 12″ long approx. 3 pound koi.

    Is the pond large enough?

    We keep the water moving through a basic filter, replace the water with city water when it evaporates and occasionally add algae reducer. The fish all appear fine


    • Koi-Care staff says:

      hmm, sounds small to me but as long as you have the filtration and water movement you should be fine (and it sounds like your fish are doing okay). I don’t think I would add any more though.

  22. Laura says:

    I am purchasing a home with a koi pond. The Lilly pads have taken over the surface. Can I just pull some out? I have no idea how to care for this pond, but I know I will love it.


    • Koi-Care staff says:

      you can pull them out if you wish but lillies are good for your pond and fish. They provide shade and cover for smaller koi. My recommendation would be to have at least 60-70% surface coverage for your pond. Obviously you will want to see your koi but you need to find that happy medium between your enjoyment of your koi and their well-being.
      Good luck and if have any issues come up there are plenty of resources on my site as well as a pretty comprehensive PDF guide.

  23. Bev Sikes says:

    We inherited a small (40 gal outdoor) Koi pond with filter system when we moved here in May. No problems until recently. We have 3 2-3″ and 3 3-4″ koi. Our ammonina % was VERY high. We did a 20% water change twice. We’ve added ‘Ammo-loc’ and its still very cloudy. How long does it take to clear…and directions say to repeat w/’ammo-loc’ every 2 days.
    We had water checked and all was good except for HIGH ammonia. We have cleaned our filter and will do so every 2 weeks. We do have plants in our pool. The algae is slimy and covers everything. We’ve cleaned it off with brush and water only. This is also a new development. Would snails help?
    Need advise on clearing up water, slime, maintaining low ammonia %, etc
    2 wks ago we could see clearly and enjoy our Koi. Not now.
    Thank you for any advise you can give us.

    • Koi-Care staff says:

      hi, so first off if i remember correctly about ammo-loc and similar products they may be sequestering the ammonia but your tests will still show it so you may be getting a false positive. Having said that however you may actually have high ammonia due to a small volume of water and a good number of fish. This pond may be have been humming along fine for the last year or so however fish tend to grow faster in the summer and a 40 gallon pond that supported 6 fish before when they were smaller may not keep up when the fish get bigger -its not a static system. 20% water changes are good but watch for pH swings and you should continue to do the water changes. The other thing I would recommend is boosting your beneficial bacteria colonies on your filter media -this will help to assimilate the ammonia, nitrites, nitrates etc. You’re seeing excessive algae because 1) its summer which means more sunlight and longer days and 2) there’s plenty of nutrients (ammonia). So in the short term i recommed (besides water changes and boosting your bacterial colonies with something like “microbe-lift”) is koi clay. You can read all about free floating and string algae in my most recent article here ( In that article i talk about the benefits of koi clay.
      The other thing I would consider for a future addition to your filtration system is a UV sterilizer -kills microbes, bacteria, viruses, free floating algae -great addition to your pond.
      Lastly I would also be concientious of how much food you are putting in the pond. If you use floating food you can more easily see how much they are not eating and feed accordingly next time.
      Good luck, Grant

  24. Dodie Bruening says:

    I need to remove my 12 6-12″ Koi from the lined pond which holds 1500-2000 gals.and clean years of accumilated sludge, and build up on sides and bottom-my concern is I have purchased a 100 gal. rubbermade structural resin tub to keep my Koi in while I do this clean up I will use a pump to ariate and keep the water moving and wonder if my Koi will be okay if this job takes more than a few hours to complete-thank you for any help/advice you can give

    • Koi-Care staff says:

      I think you should be okay with that size container- though it sounds like it will be tight.

      • Dodie Bruening says:

        Yesterday, 8/5/14 I cleaned the pond, filters and pumps,the fish did great but overnight the water has turned very cloudy–please, have you any suugstions as to what caused this and what I can do to clear up the cloudiness, and prevent this from happening again–thank you

  25. sandy.gill says:

    I have 18 and they are multiplying like rabbits any one that wants some let me know.i rescued them a year ago and they are very nice colors.their starting to pick on each other due to the fact i have to many in a 135 gallon pond..lots of babys multi colors.please help.

  26. Dodie Bruening says:

    This may be a double post because I did post a reply about my pond clean up–but want to be sure you get it so here goes, Yesterday 8/5/14 I cleand the pond, filters and pumps–the Koi did great and looked beautiful in the clear water but over night the water has turned very cloudy, can you offer any suggestions on how I can clear up the cloudiness and how to prevent it from happening again, thank you

  27. Jo France says:

    We have a 800 gallon koi pond.we use an aerator 24/7 also use Algae buster once a month. Have floating plants for shade.we had 3 koi to die in the last two weeks. They look healthy feed once a day. What are we doing wrong?

    • Koi-Care staff says:

      Well, it could really be a lot of different things that could explain these sudden deaths. What is your water chemistry like? Is there anything out of balance? You could very well have had parasites get your fish and you won’t know until you start looking at some skin samples under microscope. What kind of temperatures is your pond reaching? Plant shade is good but 800gal is on the smaller side and may be heating up pretty quick. Stress can often lead to eventual koi death. For example you may have raccoons or wading birds going after your fish when you’re not at home and causing stress (and therefore compromising the fish’s health). What about the water coming into your pond? Is it chlorinated city water? Has there been a lot of rain and runoff bringing something undesirable into your pond like fertilizer or weed killer chemical from a nearby lawn?
      When it comes to koi health, issues usually can be traced to water quality. Poor water quality by itself can lead to direct koi death as well as indirectly by allowing parasites to flourish and infect your fish. So that is where I would start if I was experiencing your situation. I hope this helps.

  28. Jessica DuFeu says:

    First of all I live in Montana so we all know that the winter’s are very cold here. I usually bring my fish in during the winter months and have them in 150 gallon tank. But this year my goldfish had babies and one of my koi’s got super big. I was thinking of leaving them in the pond with a tank heater. But don’t wanna lose my big koi. What temperature does their water need to be for them to be safe through the winter??

    • Koi-Care staff says:

      Hi, the typical practice for overwintering koi is to put an aerator at the bottom of the pond and let nature do its thing. Ice will form over the pond and they will go into a slower state with severely decreased metabolisms. Lots of fish species overwinter under ice and that includes koi. If you are uneasy about the pond icing over some people will do floating de-icers but when a pond ices over it kind of buffers the pond inhabitants from the elements of winter.

  29. Paul Carline says:


    I have a new Koi Pond approx 9000ltrs.All going well except pond is only clear for approx first 6ins.It does not seem to be Algae more a brown colour.The pond was running on an inneficient system for 4 months.System now changed to include 40w U.V.

    Tried loads of treatment but am now thinking I have been purchasing Algae removal when perhaps I should have purchased Sludge Remover.

    Any advice would be very much appreciated.



    • Koi-Care staff says:

      Paul, it sounds like you may have some much/sludge at the bottom of your pond that is getting stirred up and staying stirred up due to fish or water flow. You could look into pond vacuums -they range in price and power but that may do the trick. If its brown its unlikely to be the free floating green algae that causes “green water” for which your UV would work great on. I wouldn’t recommend getting rid of the UV though because its so useful in killing microbes. The other thing you could try first (and wouldn’t be too expensive) is something called “koj clay” (you can read more about it in my algae article on my site Its meant to kind of grab any flocculent in the water and take it down to the bottom (and subsequently koi love it for some reason).

  30. Jen says:


    For the first time we have fry :) (separated from the big pond into two smaller ponds) – they are 5mm in size – feeding them finely crushed koi food twice a day however both the ponds have become so cloudy – how do I clean without injuring the fry?

    • Koi-Care staff says:

      I don’t know how you have your ponds set up in terms of filtration and how close to each other they are but what people will often do to avoid fry getting caught up in the in-take is to use a sponge pre filter. You’re going to get cloudy water with uneaten food and a lot of bio-activity taking place. You may want to think about doing a cull, too.

  31. Bruce Dixon says:

    Is using a Pond Dye also suited for pond maintenance? I mean, many people on the internet say that using pond dye on your pond can also help prevent the growth of algae on the pond (as this the common problem when it comes to pond) please do let me know. Thank you!

    • Koi-Care staff says:

      I can’t comment on that particular brand of dye but yes, dye is an effective way of reducing light into your pond (and therefore algae). I cover a lot of algae reducing techniques in this article too.

  32. Kimi says:

    I am new to my koi pond. It came with a home I purchased. My pump motors are enclosed in a black box. When I clean out the pump boxes, there are always these little ameba looking jellies on the box. What are they and how do I stop them from forming? Also, all of my water Lillie’s have died…is this something that happens seasonally when it gets cold and will they come back when it warms up? Thank you for any help/info you can provide.

    • Koi-Care staff says:

      The jelly things? It may be slime mold but its hard to say. Is it clear? how big is each one?
      As for the Water Lily, there are many diff. kinds to include those that are more tropical and those that are more frost tolerant. My guess is that the previous owner bought the plants locally and installed them which suggests that the seller is most likely carrying the appropriate, hardy Lily type.

  33. Heidi says:

    Hi. We have a 65 gallon aquarium with two 12 inch koi and it is overcrowded, too much ammonia despite our new high quality rated 150 gallon canister filter they developed ick this week when I stopped changing 50% of their water every other day. We are having a custom 200 gallon aquarium made for us this week with an overflow and sump filtration and a uv filter. Will this be enough for them to thrive and we were considering adding one more koi. Would that be ok? Do we need a protein skimmer? Thank you.

    • Koi-Care staff says:

      hi, I’m more familiar with koi filtration systems for ponds but I have spent enough time in State aquariums husbandry dept. to say that protein skimmers are a good idea. As for the 3rd koi -you may want to let everything settle out first and see how your new set up works out (water chemistry-wise) before adding more fish. One thing you may want to keep in mind when doing pretty substantial water changes is that you run the risk of large pH swings which isn’t great for your koi. I understand you were doing it to knock down the ammonia but its worth mentioning. As a side note, you may want to give your new aquarium some time for the silicone (if used) to outgas before adding water-that typically takes about 24 hours.

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