How to Lower Ammonia In Fish Ponds (and Keep It Low)

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How to Reduce Ammonia Levels in Ponds with Koi & Goldfish 2022

lower ammonia in a koi pond
Ideally, pond ammonia should be as close to zero as possible, as the chemical is very toxic to both goldfish and koi. Public domain.

If you have a pond with goldfish or koi, you will also always have some level of ammonia, a constantly produced by-product of fish waste that just can’t be avoided. Our job as fish keepers is instead to keep the levels of ammonia as low as possible, whilst also maintaining good and stable overall water quality.

Ammonia will actually be found in all types of ponds, even those without fish, as the substance is produced during the decomposition of organic waste. In ponds without any fish, the waste would come from rotting leaves, dead insects, plants, or even visiting ducks and herons. Rarely in a pond without fish would ammonia be able to cause major issues, as the pond’s natural beneficial bacteria population would be able to break down the low quantities before they could rise to harmful levels.

However, in a fish-stocked pond, beneficial bacteria can’t always keep up with the bio-load and waste levels, so extra steps need to be taken to help keep ammonia as low as possible. Ideally, ammonia should be zero, but realistically this isn’t possible as there will also be fresh ammonia introduced by fish on a daily basis. Keeping ammonia as close to zero as you can is a primary goal in fish keeping, as this creates a much healthier environment for fish with less risk of rapid water quality changes or problems.

How Do You Test for Ammonia in Pond Water?

cloudy pond water poor water quality
Changes in water clarity could indicate a decrease in water quality, which can be determined by testing pond water. Public domain.

The only way to know for sure if you have high ammonia in your pond is to test your water using a testing kit, but there are also some common signs that could point to a sudden spike. For example; cloudy water, algae problems, or sick fish could all point to a rise in ammonia or decline in water quality that needs to be investigated.

Testing pond water for just ammonia is rare, and you’ll find most commercial test kits provide measurements for a range of different values; including ammonia, nitrites, nitrates, pH and KH. Even if tests for just ammonia were common, it would still be more helpful to perform a broad range test as it gives a better indication of overall water quality. Not only this, KH (carbonate hardness) influences pH by acting as a buffer, and pH directly affects the toxicity of ammonia in water. In other words, if KH crashes, ammonia could spike, which would cause even small amounts of ammonia to become extremely toxic. Even if you tested for ammonia and the value was fairly low, how can you be sure your pH is ideal and not contributing to more potent waste substances?

Testing your water for a range of values is always good practice, and luckily this can be carried out easily using commercial water testing kits. We recommend API Pond’s Master Test kit as it provides a great range of tests and is more accurate than strip-based testing kits. For more information on pond water testing, check our dedicated article here.

What causes High Ammonia in Fish ponds? 

1) Poor Water Filtration & Insufficient Bacteria

what causes high ammonia in fish ponds
The more fish you have in your pond, the larger your bio-load (waste), and the more filtration you will need. Public domain.

If your tests come back indicating high ammonia levels, the first thing to check is your filtration system and overall pond bio-load. Pond water should be cycled once every hour through your filter box for optimal filtration, and your filter and pond pump need to be large enough to handle this turnover. If you’re running a 2,000 GPH pump in a 4,000-gallon koi pond, for example, the pump is not going to be able to cycle the water efficiently. Likewise, if your filter box is too small there may not be enough water floor or capacity for sufficient bio-filtration to take place. The more fish you have in your pond, the better filtration you need to remove harmful substances!

Along the same lines of filtration, ponds without sufficient beneficial bacteria populations will have issues with high ammonia. Beneficial bacteria are essential to the nitrogen cycle, which breaks down harmful ammonia into nitrites and then nitrites into nitrates which are used by plants and algae.  Without beneficial bacteria, ammonia has nowhere to go, and will gradually rise to dangerous levels. New ponds often have issues with this when they’re not cycled correctly, as well as mature ponds where filter boxes are not cleaned regularly and bacteria die.

2) Excess Waste, Sludge, and Poor Quality Food

Sludge at the bottom of your pond is all the organic waste that collects in your water and sinks and accumulates on the pond liner. This includes fallen leaves, twigs, insects, fish waste, and plant matter. During decomposition, ammonia will be produced which needs to be broken down by bacteria, but sometimes waste just builds far too much and they need a helping hand. Regularly cleaning bottom muck in a fish pond is good practice, and will help alleviate some of the bio-load and improve water quality.

Another surprising cause of gradually increasing ammonia which is often overlooked is feeding your koi or goldfish poor quality foods. “Budget” fish feeds will contain a large amount of filler content, such as ash and bulking agents, which are used to cut down on overall costs. The problem with this is that fish can’t make use of these ingredients and it all passes straight through them back into your pond! Fish fed with low-quality foods will produce more ammonia and waste content in comparison to a high-quality feed.

3) Lack of Water Flow, Oxygen, and Aeration

Oxygen is essential for ponds and bio-filtration, and a lack of oxygen means beneficial bacteria cannot function efficiently. Bacteria require oxygen and nutrients to break down ammonia, so a pond should be optimally aerated to provide the maximum amount possible. Stagnant ponds with low water flow will have all sorts of issues, with rising ammonia levels being just one of them.  If you have fish in your pond, you owe it to them to provide sufficient aeration to the waters, as they can easily become sick in low oxygenated conditions. Click here for our guide to increasing dissolved oxygen levels.

Getting Rid of Ammonia in Your Koi or Goldfish Pond (Fish Safe Methods)

1) Ensure Filtration is Adequate & Optimized

filters to remove ammonia from ponds
Filters and pumps should match your ponds bio-load for optimal water filtration.

Ammonia build-up is most common in fish ponds that do not have adequate filtration, and where the pond’s bio-load (waste levels) exceed filtration capacity. Pond water needs to be cycled through a filter box every hour to maintain water quality, so making sure your pump is strong enough and the filter box large enough is the first thing to check. If your pond is 4,000 gallons you’ll need a minimum of a 4,000 GPH rated pump and a filter box that supports this flow rate. The more fish you have, the better filtration you will need to provide, and since you can’t “over-filter” a pond, the bigger the better!

Making sure your filter box and filter media are regularly cleaned is important, too, as well as optimizing your media for the maximum amount of debris removal and bacteria populations. Bio-media should be chosen for maximum surface area for the largest amount of bacteria colonies, and mechanical media should be layered with coarse, medium, and fine holes for maximum debris capture. Having just a single layer of mechanical media is often not enough for fish-stocked ponds if you want to maintain lower ammonia levels.

  • For more information on top-quality filter boxes, check here.
  • Learn more about how to clean and optimize filter media in our article here.

2) Supplement Extra Beneficial Bacteria

beneficial bacteria removes ammonia in ponds
Supplementing with extra beneficial bacteria can help reduce the amount of ammonia and nitrites in water.

Beneficial bacteria are at the very heart of the nitrogen cycle, and without beneficial bacteria, ammonia could not be removed from your water. Most ponds as they mature will establish strong bacteria populations and won’t need to be supplemented, but in some cases, it can give bio-filtration a boost. If your water tests are coming back with high ammonia readings it means your bacteria are struggling to break down the excess, so adding more will only improve water quality. Even though the issue is unlikely due to low bacteria in a mature pond, supplementing with concentrated bacteria can help reduce ammonia while you try to solve any other problems (poor filtration/aeration, etc.) Bacteria products are often added directly to the filter box or into the pond water and will get to work quickly breaking down ammonia.

They’re very useful in newer ponds, especially where beneficial bacteria have not become established, and are a key part of cycling a new pond ready for fish. For more information on the best bacteria and cycling, check our articles below:

3) Provide Oxygen and Aeration

pond air pump
Dedicated air pumps are great for providing oxygen for larger ponds or larger fish, such as koi carp.

Bacteria can’t function without oxygen and will struggle to break down ammonia and nitrites in low oxygen conditions. Likewise, both goldfish and koi require plenty of dissolved O2 to stay healthy and will thrive in well-aerated waters. A rise in ammonia could be related to stagnant water with low oxygen, so adding aerators will likely help improve conditions. Waterfalls and fountains provide natural aeration and oxygen to the water and come in both electric and solar-powered varieties. For koi ponds or heavy stocked ponds, adding a dedicated air pump can be great for a constant and stable supply of oxygen all year, providing huge doses of oxygen to both fish and bacteria. Air pumps are especially useful during winter if your pond freezes over, as they help maintain holes in the surface ice and keep a constant supply of oxygen going during the coldest months. Additionally, having a variety of plants, particularly submerged plants, can help to naturally increase oxygen levels as well as filter the water.

Combining waterfalls, fountains, plants, and air pumps together would be ideal, but any aerator is better than none in a fish pond – so take your pick! The more oxygen you can provide, the better.

4) Deter Common Pests & Predators

how ducks impact ponds
Ducks may seem cute, but they bring parasites, diseases, and huge amounts of potent ammonia to ponds. Public domain.

Ducks, geese, or even herons are all bad for ponds with fish, as they contribute to stress and also pollute the water with huge amounts of ammonia. Herons should be deterred regardless as they can cause injury to koi and will even take smaller pond fish if they can. Ducks and other animals may seem like a novelty when they first arrive but they’re actually a huge problem for ponds with koi or goldfish. Not only is their faeces (poop) a potent fertilizer packed with ammonia, but they carry a large range of diseases, bacteria, and parasites.

Ducks, the same as herons, should be deterred from landing in your pond at all costs if you want to maintain stable water quality and happy fish. This can be achieved with a mix of pond netting and specific deterrent methods, such as decoys, sprinklers, and sound systems. For more information on these topics, you can see our dedicated articles below:

5) Clean Bottom Sludge and Muck

how to lower pond ammonia
Pond vacs make short work of sludge and bottom muck, and are a good choice for larger koi pond cleaning.

Bottom sludge is natural and doesn’t always need to be cleaned for ponds without fish, but should be carefully monitored if you have goldfish or koi carp. Sludge can become very dangerous if it builds up to high levels, as it lowers oxygen content and raises waste products in the water. Beneficial bacteria will constantly be breaking down sludge, but they can’t always keep up with demand. Ideally, if you have koi especially, sludge should be cleaned out at the end of autumn before winter and at the start of spring. This ensures the best possible hibernation/torpor period and start to the following year. Sludge can be removed with either natural bacteria-based products or manual vacuums, although we find vacs much better suited for large ponds. For smaller ponds, it can simply be raked out with a regular pond net as a vacuum may be overkill.

Sludge also provides nutrients for nuisance algae, so if you also suffer with constant algae problems it may be beneficial to always keep sludge low throughout the year. If your pond has plants, having a small amount of sludge may be useful as the sludge will provide the roots with extra nutrients so they can compete with algae. Since potted plants generally have their own substrate and can also suck nutrients directly from the water, it’s up to you whether you clean all sludge or leave a little behind.

6) Carry Out Regular Water Changes

water changes to remove ammonia
Water changes will help remove ammonia, as well as replenish minerals and alkalinity. Public domain.

If you have koi or goldfish, you should be carrying out regular water changes to help replenish trace minerals, alkalinity, and remove harmful substances. Contrary to common belief, water changes are not bad for ponds, and they should actually make up part of every fish keeper’s regular maintenance routine. If you’re currently suffering from high ammonia parameters, ask yourself this – when was the last time you carried out a large water change? If the answer to this is a “long time ago,” or “never,” start changing that water today!

Performing a weekly 10% water change will not only help remove a large chunk of free-swimming ammonia and help get your parameters down, but it will also replenish essential minerals and alkalinity. Minerals such as calcium and magnesium are important to fish health, in particular the regulation of salt within the blood, and they get these directly from the surrounding water (and food). Likewise, alkalinity is important to prevent sudden swings in pH and works as a “buffer” to prevent this from happening. Alkalinity, or KH, comes in the form of carbonates, such as calcium carbonate, and needs to be replenished regularly as they become used up by acids (rain) and beneficial bacteria (yep, they love carbonates, too!). Check our out guide below on how to perform water changes in ponds for the best results:-

7) Invest In A Top Quality Fish Food (& Don’t Overfeed Your Fish!)

The amount of ammonia in a pond is directly related to the amount of fish waste, so keeping waste as low as possible is ideal. Good quality feeds will have lower “filler content” and more ingredients fish can actually use, such as protein, fats, vitamins and minerals. Investing in good quality fish food will reduce the amount of waste your fish produce, and also enhance the growth, color, and immune systems of koi and goldfish. Top feeds also source their protein from aquatic cultures, such as krill, anchovy, and fish meal, making them more optimal and tastier – which fish will love! For more info about selecting the right feed and what ingredients to watch out for, see our full guide here.

Also, it should be noted that you should not overfeed your fish as any leftover food will simply sink and contribute to bottom muck. Since quality food is also high in protein and nutrients, any left around can cause issues with cloudy water and algae bloom. Keep an eye on your fish and make sure to monitor feeding to ensure they’re eating all their grub!

28 thoughts on “How to Lower Ammonia In Fish Ponds (and Keep It Low)”

  1. I live in ontario canada and, we have fluctuations in temperature. I have a small pond (5’×8′ w depth 4′) out pump filter and water fall is off. We have a bubbler and de icer going. At the moment we have high amonia levels. I added salt and there was some improvement. My husband wants to skim the bottom of the pond where the five koi fish are hibernating. I’m worried this will make matters worse. Any suggestions or thoughts? We are going to do a partial water change too. It is still too cold to add our pump and filter.
    Regards Niamh

    • Hi Niamh,

      What’s giving you the impression of high ammonia? Have you performed a water quality test? Or are fish becoming sick?

      Cleaning the bottom of the pond in winter, especially without filtration, isn’t recommended as you’ll actively stir up all the nasty substances that have been decomposing slowly over the season. In warmer seasons the koi would tolerate it, but as they’re in hibernation, it will place a lot more stress on them and likely only increase the amount of free-swimming ammonia in the water.

      Water changes are indeed the best way to go in your situation. Personally, I’d start with a 20% water change and test for ammonia again the following day. If ammonia is still high, perform another water change and re-test. As soon as ammonia has been sufficiently reduced, a 10% water change weekly will likely keep levels safe until spring cleaning starts.

      Adding fresh water through water changes will also help replenish pond alkalinity/KH, which is very important to prevent dangerous pH fluctuations. Beneficial bacteria also require good alkalinity (carbonate) levels so they can continue to break down waste, even in winter.

      Hopefully the water changes do the trick. Let me know how things turn out!

      • Hello,
        I have had my pond for like 4 years in my font yard. It’s in ground and about 750 gallons with several koi. I just built a above ground bog filter, yet to plant the plants. I turned off my previous filter and just ran my new bog filter with the pea gravel.

        Next morning i see foam and my pond is dirty and the fish thrashing. The fish did stop thrashing this afternoon. What do I do? Beneficial bacteria on the way, shipment arrives monday.

        • Are you sure they are not spawning ? The foam can be this the thrashing also , april and may are peak spawning season temp changes in water can also trigger it in spring

  2. Hi I have a very high ammonia level have done 2 50% water changes and it still high I’ve lost 6 koi and I am worried I will lose all my other big koi can someone help me plz

    • Hi Paul,

      I’m really sorry to hear that! Nothing is worse in this hobby than losing fish.

      Could I ask where are you getting your water from? Is this your mains supply or from a natural source, such as a well?

      If ammonia is still testing high after 2x 50% water changes, the ammonia may be in the actual water supply itself. You can determine this by directly testing the mains supply with a water quality kit (same as the pond kits) or contacting your water company to confirm.

  3. hi i lose 4 koi on my pond because of ammonia i guess, so i built a filter media topped with charcoal/carbon then gravel and the water is now clear.
    I also added lilies and lotus.
    Is that a good sign that ammonia levels are lowering? sorry i dont have a test kit 🙁
    im planning to add lava rocks on the filter media, is that safe?

    • Hi Migs,

      I’m very sorry to hear about your koi.

      Any extra filtration (and additional surfaces for bacteria to colonize) will always be beneficial, but without a proper water quality test, it would be very difficult to determine if things will improve. A water quality test will help you pin-point the problem, as it may not even be ammonia that is causing the issues. After performing a test (this should be a top priority), you can then determine what the next steps should be to counter the problem.

  4. Hope you can give me some answers to my pond crashing. I live in Mass. and for the second year in a row my pond has crashed. I don’t understand what is happening.
    I have a 2000 gal pond and run two four thousand gal per hour pumps with two 4000 gal UV filters. I use beneficial bacteria, charcoal, and feed very carefully. I do regular water changes however when ammonia gets very high the water change can be over 50%. The climbing in ammonia and drop in Ph seems to start around May 1st and continue until the end of June. My thoughts are that the pollen has been incredibly high the past couple of years and the water ,like my car, has been yellow for weeks. One last thing, even thought the water quality has been poor the fish are mating. This adds to more organic waste in the pond. I would think if the Ammonia and Ph crashed the would not be active. All fish are active and eating.
    I could really use your insight.

    • Hi Bob,

      Really sorry to hear about the problems you’re having, but it’s good to know your fish still seem to be doing fine under the circumstances!

      That does sound strange, but it could very well be related to the large amounts of pollen and organic debris entering the pond within a short period of time. Could I ask what your water quality test results are showing before and during these “crashing” periods? In particular, could you let me know the parameters for ammonia, nitrites, pH and KH/Alkalinity?

      I do have some ideas here, but I’d first like to know more exact parameters so I have a better idea of the actual effects taking place on water quality.

  5. Thank you for getting back to me. this really has me baffled.

    My reading for Ph before the crash is right at 7 and the KH .25 to .50. When it crashes the Ph will go to 6.2 and the Kh around 8. You would think it would be enough to kill the pond. This happens in a matter of a couple of days. As a matter of fact yesterday the Ph was coming back around 6.8 and this morning it was 6.2. On a good note the Kh was much lower around 1. I try to always check the reading the same time each morning about 7am. I have had the pond close to 20 years and this has only been happening the past two years. I have 20 fish ranging from large adults to fingerlings. Adding more beneficial bacteria has been bring the Kh down. I really don’t want to raise the Ph much until the ammonia is just about gone. I know their mating is adding more organic matter to the pond and they are still going strong so something must be right. My water flow through the filters is around 750 gph. There are two filters so turn over is around 1500 gph. the two pumps are rated at 4500 gph so there is a lot of water movement. Right now the water is crystal clear and the pollen has subsided. I’ll have to see how tomorrow mornings water check goes.

    • Hi Bob,

      Thanks for letting me know the parameters! I’m assuming that KH reading is in degrees of hardness (°dHk)? If so, personally, I’d say your KH is far too low outside of these “crashing” periods, and actually just about right during (8°dHk is actually ideal for koi). Alkalinity/KH is essentially a measure of your waters ability buffer acid (hydrogen ions) and prevent swings changes in pH, and you’d ideally want a KH reading within 7-11°dHk for the most stable water quality and fish health. You can read more information on this here (table at the bottom for quick parameter ref):

      To quote myself from the article above – “During the day, plants will carry out photosynthesis and absorb carbon dioxide from the water, which in turn, reduces the amount of carbonic acid and causes a rise in pH levels. During the night, plants will switch to respiration, consuming oxygen from the water and releasing carbon dioxide, causing a return of carbonic acid and a drop in pH levels. Carbonic acid (H2CO3) is a combination of carbon dioxide (Co2) and water (h20), and is the primary contributing factor to pH changes in fresh water ponds.”

      Your higher pH towards the end of the day and lower pH in the morning is likely explained by the above, which is a natural process that can occur even if you have no potted plants or noticeable algae (microscopic plants all over your pond liner, rocks, and equipment will also contribute). Since in summer you’ll have far more of this microscopic growth, it seems plausible it could be the cause. However, even these changes in pH can be lessened by having a stable KH/Alkalinity water parameter.

      The reduction in KH you’re seeing in the morning also makes sense, as the additional acids produced in the night are being buffered by your water’s alkalinity, in effect reducing the parameter. Additionally, beneficial bacteria also require carbonates (KH) to process waste compounds, so adding more bacteria will reduce your KH, but if you do not have enough carbonates (KH) in constant supply, bacteria will not be able to function efficiently. This eventually results in bacteria die-off and possible ammonia spikes. It’s all a very fine balance, but one where KH/Alkalinity is very important!

      Your initial spike in KH is more difficult to determine, as often this would be associated with a rise in pH (carbonates/bicarbonates are base), not a drop! Can I ask what test you using to determine KH? Also, what is your General Hardness (GH) parameter showing? Finally, how hard is your water and what is your source (mains supply or well water)?

  6. I am not sure of the water hardness in the area and I am not sure of what is in all of rain water. I say this because we have been getting more rain than usual. I will purchase a testing kit with a better range and be able to give you more information. I really didn’t consider the water hardness. It could be a major contributing factor I have over looked.

    This morning I tested and the ammonia level has dropped to .50 and Ph was 6.8. Yesterday I added 3 lbs of charcoal along with an addition dose of beneficial bacteria. It seems to be going in the right direction.

    I can’t thank you enough for your advice.

    • Hi Bob,

      No problem! Always happy to help if I’m able. Glad to hear your water parameters are stabilizing somewhat this morning! Fingers crossed they remain more stable over the next few days, too. Let me know those updated parameters when you have them, or if you discover anything new. I’m very interested to know how this turns out.

  7. Hi Chris,
    Just wanted to let you know that it is truly refreshing to find someone that not only has knowledge but someone that will actually take the time to answer questions. I am not sure of your location but I am just outside of Boston and there are no real aqua supply stores left in the area that carry the pond supplies, or persons to give advice, that is needed. Simply finding water plants can be extremely difficult.
    I have more testing supplies on order and will follow up as soon as I can.
    Thank you again for all of your help.

  8. Hi Chris
    I did some samples and this is the reading I got this morning.
    Ph Ammonia GH Kh
    Rain water— 6.0 .25
    Tap water — 8.0 .25 5drops 17> never turned from blue

    Pond —– 6.6 .50 2drops 4drops
    (35.8ppm) (71.6 ppm)
    I use the API test kits.
    The ammonia is dropping. The Ph is still a bit low but it rained again last night. I did a 10% water change today. Fish are all active and show no signs of distress. Hope this can give you a better idea of what is going on.

    • Hi Bob,

      Thanks for getting back to me with the updated parameters! I’m assuming by looking at the numbers, such as “6.0” and “0.25”, these are for pH and ammonia, respectively?

      If these are the pH and ammonia parameters, could you also post the GH and KH data if you have it? Just tap water vs pond water would be enough for those parameters. There should also be a conversion table in the instruction sheet for converting all parameter data to ppm (or equivalent), which makes it easier to work with.

      Also, good to know the ammonia is going down and fish are happy! Always a good sign.

  9. Hi Chris
    Did my morning check and these are the numbers.
    Ph 7 Ammonia between 0 and .25
    Kh and Gh both 5 or 89.5 ppm

    Looks like things are starting to settle. Same thing happened last year in the same way.

    • Hi Bob,

      Hmm, your GH and KH are actually ok (maybe a little on the low side). In my first reply I assumed your units were in degrees of hardness (°dHk), and I didn’t realise you were giving the test kit result numbers. Your ammonia readings are nice and low, too!

      Could I just confirm again – before the ‘crash’ periods, your pH is higher and your KH is very low? And during the crash, your pH drops and your KH goes up rapidly?

      This is the part that confuses me, as the compounds that make up KH (carbonates/bi-carbonates) are base, so they should push the pH up as their concentration in water increases. If your pH drops rapidly in their presence, it often means they’ve been exhausted due to excess acid in the system and the KH will effectively drop alongside the pH.

      I’m inclined to say that if your fish are happy and healthy, just leave things as they are and continue to monitor the situation. Fish often become easily stressed during pH changes that they can’t tolerate, so if they’re eating, swimming, and even breeding without problems, I’d say these changes are safely within their tolerance range and not something that may need fixing. The only way to reduce the amount of pH change would be to increase KH/Alkalinity (even double your parameter is fine), but I can’t advise that as I’m still unsure why your KH is sky-rocketing during those crashing periods. Trying to increase this parameter without knowing the full story could cause even more problems, so I think it may be safer to just let things play out for now unless you find out more.

  10. Hi Chris
    Reading this morning were the same as yesterday. Ph 7 Ammonia .25 Kh and Gh both at 89.5 ppm.
    I think it may be a combination of issues. The high acid of rain water, the high Kh in tap water, and the huge amount of pollen.
    Over the past few days I have done more water changes, added more beneficial bacteria, and added more charcoal. The parameters seem to be stabilizing.
    I think you are right let it play out for awhile. I will give you and the pond a chance to rest.
    Can’t thank you enough for being so helpful and concerned. I’ll check back and let you know what happens.

    • Hi Bob,

      Yeah, I think it’s one of those situations where it’s probably best to just let our fish do most of the reporting, so to speak. If our fish are reporting that they’re happy and healthy (swimming, eating, breeding etc.), we can assume the water quality changes are not affecting them too adversely and no immediate fix may be needed. If, however, they begin reporting that they’re unhappy (changes in behaviour, feeding, color etc.), we can certainly look deeper into things and possibly make some adjustments. I think you’re already doing a fantastic job right now with water quality and monitoring, so there is little left to do but wait and hope things eventually stabilize.

      And it’s no problem. I really appreciate you taking the time to comment and share your story and experience. Maybe our conversations will help other readers, too!

      Yes, keep me updated if anything comes up! Really hoping things stabilize and balance out for you and your koi in future.

  11. Hi Chris,
    Just a follow up. All numbers have been holding and well within safe limits the past few days. The fish are active and eating and the water is crystal clear again.
    I was thinking about the time before everything crashed and I recall the water becoming more foamy than usual. Do you think It could be a sign that the water is becoming harder and more organic matter in the pond because of the high pollen count?
    One last question. What is your opinion on adding salt? I know of people that swear by it and others that want no part of it.
    Thank you again.

    • Hi Bob,

      Sorry for the slow reply. It’s been a busy week. Glad to hear your water parameters are still holding strong!

      The extra organic matter in the water could be causing an increase in foam, but if your ammonia readings are still low, the foam is most likely harmless and more of an eye-sore than anything. You could use de-foaming products to remove the foam if it’s a huge issue, but I’d recommend just letting it resolve itself. You can read some more info on foam specifically here –

      In regards to salt, what are you looking to achieve by using it? Short-term, isolated salt baths can certainly be useful for some types of infection/illness, but I definitely wouldn’t recommend simply increasing the entire ponds salinity levels, as this can be very dangerous. In fact, studies have found that even a tiny amount of salt (less than a gram per liter) can have immediate lethal effects on freshwater fish, bacteria and aquatic wildlife. Source:

  12. I have been reading the posts, hoping for insight to our own problem of ammonia readings being too high. I have a large koi pond, shaped like a creek, about 60ft long with small pools at both ends covered by caves with waterfalls. I have 2 large airstones, 5 pumps, 2 for each waterfall and the other 3 for the 3 five gallon sponge filters, which I clean every 2 weeks. I don’t know the exact gallons for the creek, guessing over 3000 gallons. We have about 60 to 70 large koi. They began spawning less than a week ago and the creek was just bombed, nuked, with their eggs and so forth. I cleaned all the filters and changed out the air stones. We visited a local hatchery here in Miami and they warned us about high ammonia and suggested a large water change and water conditioner to remove ammonia. We tested the water, which came up a 5, in the danger zone. I did 3 water changes over 3 days just to get it down to a 3, lowest # for the danger zone and used 2 gallons of water conditioner to battle ammonia.
    We have had the koi for 7 years but never has the spawning been awful and polluted the water like this, it is crazy.
    Any ideas why this spring it became so extreme???
    Normally the filters work great, almost crystal clear water, especially after filter cleaning day.

  13. Thanks for writing it out! I always make sure that my fishes are healthy and happy in their artificial environment. With the help of your guide, my fish will surely be forever thankful. 🙂

  14. I always make sure that my fishes are healthy and happy in their artificial environment. With the help of your guide, my fish will surely be forever thankful.

  15. I always make sure that my fishes are healthy and happy in their artificial environment. With the help of your guide, I will be getting the better rather than the latter.


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