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How Do I Get Rid of this Terrible Odor Around My Pond? – Pond & Lake Q & A

Picture of Gas Being Released from the Pond.

Pond & Lake Q & A

Q: I have an awful smell around my pond. What is causing it and is there anything I can do to get rid of it? – Hailey of Nebraska

A: I think we’ve all experienced this at one time or another. We’re outside, enjoying the spring breeze and decide to go wandering around the pond to maybe spot some frogs or to feed the fish. All of sudden you go to breathe in the fresh air and you quickly realize that it’s not so fresh after all. Your nostrils are engulfed with a distinct musky odor as you retreat away from the pond. Is it gas? Do you call the fire department? No. Call The Pond Guy®. That sulfurous smell that finds its way around ponds is a common byproduct of a pond that is not aerated.

Non-aerated ponds stratify (layers in the pond have distinguished temperature differences) in the summer and winter, locking the bottom layer of water away for months. With no circulation, the oxygen is quickly used up down there, resulting in an anaerobic (functioning without oxygen) digestion process that is loosely equivalent to that of a cow’s stomach. Slow-moving anaerobic bacteria on the bottom use enzymes to ferment and digest the muck on the bottom. These bacteria produce waste products including carbon dioxide and hydrogen sulfide (rotten egg smell).

Most of the year, an un-aerated pond will smell fine because this buildup of nasty gasses stays locked away on the bottom. It is when the pond turns over (Spring/Fall temperature shift, strong weather event, etc.) that the foul-smelling gasses are released. Surprisingly, the foul smell is the least of the pond’s problems at this point. The release of this gas also signals that the inhospitable water that was stuck underneath has now mixed into the upper part where your fish are living. Wacky pH shifts, dissolved oxygen crashes, and algae blooms are a few of the byproducts of turnover, all of which have fish-kill potential.

The solution? Aerate like it’s your job! An Airmax® Aeration System will keep the pond in a permanent state of motion, continuously venting gasses and providing oxygen to the bottom sediments. This allows the aerobic (good, oxygen loving) bacteria in the pond to inhabit the bottom sediments and work away at that ugly muck layer. Aerobic bacteria work similarly to plants in that that they use up the bad gasses and muck, and give off a little oxygen in return while working much more quickly than their anaerobic (cow’s stomach) counterparts. Supplement these bacteria with MuckAway™ Natural Bacteria or PondClear™” bacteria that will accelerate the decomposition process. Remember, keep that pond moving to keep that pond healthy and odor free.

POND TALK: Have you ever run into this odor problem? Tell us about it. What are you doing or have already done to get rid of it?

31 Responses

  1. Yes I’ve had this happen with my koi fish pond. I hav had tried many things but they were only brief fixes like clean filter add shock ball. When I finally added an aerater my pond cleared up,less algae and the smell improved. It happened again when I removed the aerater and added live plants. The plants started dying,algae started growing, my pond was murky and stinky. Cleaned the filters and added an aerater back and the problem is working itself out again. The fish actually live the aerater and become more active. Just though I’d leave the comment because I was constantly messing with my pond trying to figure out the problem and it was actually a simple fix with the aerater. It was a little pricy but well worth it!!!! Hope this helps someone

  2. I have a fish pond and people are living around. What do I do to stop bad odour from the waste water. It’s smell is terrible.

    • Hi Sylvester – Removing the source is always the most helpful but if that is not an option products such as PondClear™ and MuckAway™ work to breakdown the organic waste and help eliminate odors. Aeration will also help to release the gas buildup that occurs from the accumulation of rotting material.

  3. HELP! Our pond is on a segment of land with no access to electricity. But we like to go there as a get-away to swim. What does someone in this situation do to aerate a pond or at LEAST deal with the muck? I hate to lose our favorite swim hole. We have had the pond 16 years and this is the 1st summer with this horrific odor..maybe the high humidity (There are no fish and it is approx. 13′ deep in center and approx. 1/4 acre; it is spring fed)

    • Hi Pauline – You can still aerate with a windmill. It isn’t as consistent as an electric aeration system but will still provide circulation at the bottom of the pond. This will initially cause some cloudiness and may increase the odor as the gas is actively released from the accumulated muck, but over time it will clear up. You can still use natural bacteria like MuckAway™ on its own to reduce muck in the pond, especially around the beach area, however the addition of aeration will speed up the process greatly.

  4. Pond fish food will also create a strong smelly odor. You will notice it if you ever add some to a fish tank. I gotten some from a Zoo and add it to my fish tank of goldfish. The room smelled badly for the whole night. Add some pellets to a bucket of water and see if it smells later.

    • Thank you for your response. Yes, the fish food will have an odor. From my own experience the flake style or smaller containers of fish food for aquarium fish have a much stronger odor than the pellet food for pond fish. Also since most ponds are outdoors the small amount of odor is usually not noticeable unless large amounts of food are left unconsumed in the pond.

  5. Greetings,

    I work at a fish hatchery and we have a settling pond on site where all the effluent and fish waste settle out. As one could imagine, it smells. Currently, we do not have an aeration system in the pond because there is concern that with the large volume of organics going into the pond daily, it will do very little to help. We have tried adding microbes, extra oxygen to the effluent, and have pumped out several truck loads of the sludge in hopes to reduce the odor. None of these things have made a noticable difference making it hard to justify spending a large amount of money on continued treatments and pump-out costs. During our peak stocking season in the spring/summer, an extra 500gpm of flow goes to the pond which does seem to help. However, we are not able to dilute the pond year round. Any thoughts?

    Kind Regards,


    • Hi Megan – With that large volume of waste being contributed on a regular basis it would be hard to see any overnight type results. Aeration and natural bacteria are a regular maintenance treatment and must be done consistently to offer long term results. I would recommend establishing the aeration system first and then continue the use of natural bacteria. In a situation where a lot of waste is being produced the pond likely has a very low dissolved oxygen level creating an anaerobic environment in which the beneficial bacteria are not able to thrive. Aeration will provide the circulation and means for the gases to be released from the pond while bringing oxygen in. When the oxygen level rises the natural bacteria will be more efficient and decomposition of waste will increase. Aeration, unlike other treatments, can be utilized year round as well. When you add the extra water that does help with circulation but if it is not pushing from the bottom of the pond up it is not really doing much to release the gases from the water or increase oxygen. If you know the pond’s size and depth or could e-mail or call with the location we can measure it and discuss in further details a treatment program that would work for you. pondhelp@thepondguy.com or 866-766-3435. In the meantime you may want to watch the video on Airmax Ecosystem which explains our philosophy on the use of aeration and natural treatments as well as Aeration Installation so you can see how these systems are installed. I hope this information helps!

  6. I live kind of close to a very large pond, lately the highway that runs by it and now my neighborhood has had a weird, musty, “cellar floor” type of smell in the air. I have called the environmental police and sanitation departments in my city, still waiting for an answer to this smell. Any ideas what this could be and can you tell me the name of the department or agency I should call to report this unpleasant problem further? Also, what should or can they do to rectify this problem and does this smell also mean that the air is not safe?

    • Sorry Michael, we cannot help you with this. There are too many factors that come into play. I would continue to call your local EPA or local branch of Department of Natural Resources.

  7. We live a few feet away from a man made pond (formed by a dam on a river). This summer, the dam owner is emptying the pond to repair the dam. Process would take ~ 3 months. What impact should we expect? (smell, animals, etc.) Anything we can do to prevent / mitigate the impact? Thanks

    • You may notice that some of the wildlife moves to other locations temporarily and will mostly likely return once things are back to normal. If muck has been accumulation you will probably notice some odor from rotting material being broken down. Raking out any dead debris will help to reduce this when water returns to the pond but nothing else needs to be done without the pond being full of water.

  8. Hi,
    I just recently built a 6-7k gallon koi pond which currently has no fish in it as I figured I would wait until the spring before introducing fish to the pond. But there are two ducks that have access to the pond. I still have my pumps and two large aerators going even in these winter conditions (low around 25F today). The pond hasn’t frozen completely over since I have these aerators, pumps and a biofilter/waterfall that continues to oxygenate the water but today I noticed a strong sulfur smell emanating from my shed which is next to the pond edge which houses the Pondmaster aerator. Today, the pH is 7.6-7.7, Ammonia is 4ppm, nitrate and nitrite is both 0. I assume since the water is just above freezing, the bacteria in my biofilter hasn’t quite grown into the numbers that it needs to handle the waste from the ducks. Also, there are no plants in the pond. In this situation, what can I do to lower the ammonia level and rid of the sulfur smell? Also, I have added approx 200lbs of solar salt over the course of the past 4 months to the water to create a briny water so I havent needed to heat the pond all that much. Please advise me on how to proceed. Thanks.

    • In the cold winter months there is little you can do to establish much bacteria growth, keep the circulation going and rest assured that the bacteria will begin to increase as it gets warmer. Since this is a newer pond it looks as though your pond is just going through its natural establishment cycle. You may see the ammonia continue to increase and then it will decrease at which time you will begin to receive nitrites. Once nitrites have risen and fallen you will start to see nitrates. At this point the pond has cycled and will be ready for your fish!

  9. aeration is the best solution. Potassium permanganate may be one of methods to reduce odor.


    • Hi Bill,
      Chara is not a pond weed but a form of algae. There are a few distinct qualities for Chara, which separates if from pondweeds. Chara has a “skunky” or musky smell, which you could smell if walking close by the pond and Chara is not rooted into the pond, like pondweeds and it is very easy to pull out of the water. It also has a very gritty feel when you rub it between your fingers.

      It would require an algaecide, such as Cutrine Plus Granular for treatment. If you are on a waterway that connects to public water, you would need to check with your Department of Environmental Quality or DNR for any permits that are required and what chemicals that you are allowed to use.

      I have also included a link to another Pond Blog question that discusses odors that are not related to Chara.

  11. I have a water fountain in my office at work; and I’ve been trying to find some kind of solution to help with the smell. When I leave for the day I turn the fountain off and back on the next morning, however on Fridays when I leave for the wkend and come back in on Monday’s the fountain smells like rotten eggs when I plug it back in. This is bad for our clientelle. Any suggestions? I called Lowes and have tried several things but I would really like someone who know what their talking about to help. THANKS

    • In regards to the rotten egg smell in your water feature, this is most likely caused by a build up of organic debris that is slowly decomposing. Has anyone done a clean out of the fountain? Products such as Barley Straw Extract and Liquid Clear will also help to remove the build up of organic material and reduce the rotten egg smell. If you like you can respond with more details about your fountain and we can provide further recommendations. Some helpful information would be the setting (indoors or outdoors), if there are any fish present in the feature and approximate length and width of the basin containing the water or approximately capacity of water. You can also click on the product names above for a link to the products on our website.

  12. i bought my house 2 years ago and the people before didnt take any care of the pond at all.at the worst spots there is about 2 ft of muck the pond is about 3/4 of acre i am trying to do what i can with a fountain and chemicals but its so mucky i cant tell the results should i keep in one area? we would like to use this pond to swim what are your sugestions? thanks

    • As for the muck, I would start by raking out as much as you can first using a Pond & Beach Rake. After that you can use MuckAway to continue to breakdown muck and other organics in the pond to help prevent future buildup.

      As for the fountain, they are usually best placed in the center most part of the pond if you are trying to use it to aerate, however, fountains are not the best aerators when the depths of your pond are deeper than 6′. If this is the case I would utilize the fountain for more of a decoration and use an Airmax Aeration System to aeration and circulate the pond.

      Hopefully this helps.

  13. Sure, aeration helps a lot; but unless you fix what’s causing the problem, you’re probably wasting your effort. Think about why there’s stink in the first place. Most probably your pond is overfed with N and P leaching from the fertilizers that makes your lawns green. I aerated, added beneficial bacteria, and stopped using fertilizers. Did this for 2 years. My pond has been stink free and the water clear for at least 3-4 years since. Now, I don’t even aerate. Just don’t feed the pond!

    • Tony,

      Great comment, my only thought is to keep aerating for the overall health of the pond and more importantly the fish. Other than that you are absolutely right, don’t feed the pond or keep it at least to a minimum.

      • What do you mean by “don’t feed the pond”?

      • Julie,

        What I mean by feeding a pond is simply limiting the amount of organics that go into the pond in the first place. For instance grass fertilizers for your lawn, grass clippings from cutting the grass, leaves & twigs that fall from the trees. These organics, once they get into the pond, begin to breakdown into “muck”, which is what we were referring to above.

        Hopefully that makes sense. Thanks for the comment!

  14. I have an odor around my pond sometime and my pond is aerated. What could my problem be?

    • Richard,

      Another possible reason for the odor smell with be from a form an algae called chara. Chara has a musky smell to it and at times can be pretty smelly. I would walk around the edges of your pond and look for something that looks like this: Chara

      Hope this helps!

  15. Do you know an good dock suppliers?

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