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Here's an article that reiterates what I've been saying

Discussion in 'Water Features' started by Victor, Mar 11, 2006.

  1. Victor

    Victor LawnSite Bronze Member
    Posts: 1,637

    Joe Cuny wrote this article, addressing a major design mistake a lot of pond builders make. The article is titled, "A Major Design Flaw."

    "It has been brought to my attention that some pond builders (both Koi and water garden) apparently are not familiar with basic pond design. In particular, I am referring to the use of gravel and rock inside the pond. As anyone who has been a pond keeper for a few years knows, that is a real no no. Possibly this practice is a direct carryover from the aquarium 'under gravel' filters, but it is a wrong application of the concept.

    The problem is that the gravel and rock form a dead zone, more appropriately called a stagnation zone. Whether the pond has fish in it or only plants, there are all kinds of organic material produced in the pond. This organic material gets trapped in the stagnation zone and guess what happens? It stagnates! Since the water does not circulate very well in this zone, the water is deficient in dissolved oxygen, and the organics are processed anaerobically. In other words, the organic material rots or putrefies.

    The end result of such putrefaction is the production of noxious gases and disease organisms. I do not know what effect these would have on plants but they are deadly on fish and are very unaesthetic. In time such a pond would smell like a cesspool! This is exactly what happens in an aquarium if the under gravel filter is not cleaned regularly. Even with oxygenated water flowing through such a filter, there are dead spots where the water does not flow and these have to be cleaned, usually with some type of vacuum or siphon system.

    If it is necessary to put rocks on the bottom of a pond, possibly to simulate a natural stream, they should be well separated and bedded in mortar to allow flow around them and to eliminate pockets where debris could accumulate. The amount of work necessary to properly imbed gravel probably eliminates the use of gravel. If it is thought that the gravel will function as a filter, it should be placed such that it can be fairly easily cleaned. Despite claims made by various people, all filters must be cleaned. The only possible exception is the trickling filter type that is self cleaning, but in the process dumps the waste into the following stage where it must be captured and disposed of.

    I have seen gravel filters built into a sump in the bottom of a pond. Such a filter is almost impossible to clean, and the resulting pond does not provide a healthy environment for the fish. With such a filter in a water garden, I would expect the same type of problems. I realize that many people believe that the root system of the plants provides space for the organisms that degrade the organic material, but this is not a suitable filter except for those organics that are soluble. Even these, when aerobically digested , result in material that falls to the bottom where it joins the leaves, stems, decaying roots, and so forth and then putrefies.

    Joe Cuny is a founding editor and contributes to KOI USA since its beginning, over 20 years ago".

  2. Victor

    Victor LawnSite Bronze Member
    Posts: 1,637

    "Some time ago I discussed a practice that seemed to be developing on the East coast. I understand the same practice is now showing up on the West coast. This has to do with the placing of rocks, stones, and/or gravel on the bottom of a pond: it is called aesthetics because it simulates the appearance of natural streams.

    Don't get me wrong, I am not against aesthetics. Yes, I know that scientists, engineers, and so forth are supposed to be cold, calculating things with no interest in the arts, but this is not necessarily so. Even though I am aimed at the engineering aspects of koi husbandry, after many years of koi shows I would hope that some of the aesthetic aspects have penetrated my skull.

    Also, I believe in the truth, whatever that is, and I do not believe in shoving that truth down people's throats. I like to be reasonably sure that people have the facts (not necessarily my facts) before deciding on something. The following are, to the best of my knowledge, the major facts concerning rocks in the bottom of a pond. I am sure that some vendors have their own set of facts; whichever set you want to believe, is up to you.

    Whether the pond is constructed of concrete, fiberglass, or a liner, rocks on the bottom can be bad for your koi. Note the conditional phrase "can be bad" because that is the type of thing often ignored in engineering statements. The various conditions are ignored because people want a simple answer, not one that requires some effort to understand. Come to think of it, the same thing often happens when some koi get sick or die. Usually the owner wants a simple answer, no complications. Unfortunately, life is not simple!

    Now to the question, what's wrong with aesthetic rocks in the bottom of a koi pond? The first reason is the simplest and not even engineering. When koi scratch or flash as they sometimes do, they rub on the bottom. Any projection on the bottom can cause damage to your koi.

    For the engineering answers, we have to consider some of the differences between our ponds and natural streams. In particular, why do we use biofilters on our ponds? Obviously, we use them to process the waste products of the koi and thereby ensure that the pond water is safe. To put it bluntly, we don't want our koi swimming in their own toilets!

    How does this relate to rocks on the bottom of a pond? The rocks interfere with the flow patterns of the water and provide pockets where solid waste can accumulate. (Incidentally, the same problem occurs with a thick layer of algae.) Each of these pockets then becomes an individual sewage treatment plant. Since these rocks simulate those in the natural streams, we have to ask, why are the rocks in the pond different?

    At this point we could chicken out and simply state the answer but let's take a minute or so and slightly expand our engineering knowledge. When engineers design a model, they run into compatibility problems. Real systems such as buildings, machines, boats, ponds, and so forth, are influenced or controlled by a number of things. Most of those things follow different laws-laws that are incompatible in designing models. When the model is designed, the designer must select the aspects to be considered and essentially ignore all others.

    Similarly, if you designed your backyard to simulate a specific Japanese garden, you would not simply scale it down to fit the yard. A scaled-down garden would result in a pond that is probably too small, along with small koi, trees, and so forth; everything would seem inappropriate for a backyard. Again, you would not scale it down but you would design a garden that would give a feel for the original. In other words, your modeling would emphasize the aesthetics of the garden. Now back to the original question, what's wrong with aesthetic rocks in the pond?

    In natural streams, the water velocity (actually speed) is significantly higher than in a typical koi pond. This means flow strength and patterns around the rocks are totally different in the two cases. Because the flow speed and rock sizes in the pond could not be modeled, the pockets of debris around the pond rocks are of different relative sizes and tend to be more stable than in a stream. Additionally, the adjacent water contains significantly lower dissolved oxygen. Note that this is in the pond, not in an aerating stream feeding the pond. In the pond, these sewage treatment plants almost certainly function anaerobically, producing unwanted gasses, bacteria, and so forth, whereas in a natural stream, the treatment would be more aerobic because of the higher speed and turbulence.

    If the rocks were embedded to reduce the possibility of dead pockets, the above engineering reason against the rocks would be eliminated. Such embedment, however, could cause problems of its own. Let's say that you have a liner pond and apply a thin layer of concrete on top of the liner to embed the rocks. What problem can that cause? Over time, organic material dissolved in the water can find its way between the concrete and the liner. Once again, this is an anaerobic environment so the decomposition of the organic material (it's rotting!) produces gasses. Eventually these gasses lift portions of the thin concrete and fracture it. The fractured edges are very bad on flashing koi! Of course, a thick layer of concrete can eliminate this problem but the cost of such a layer usually eliminates the benefits of a liner pond.

    Another condition is sometimes used to prove that the bottom of a pond should have rocks. This condition is the under-gravel filter that is common in aquariums and is occasionally seen in ponds. Note that in both of these cases, they are called filters because they actually are filters, not simply rocks on the bottom. The re-circulating water is drawn down through the rock filter, carrying the fish debris along with oxygenated water. Even in these systems, it is sometimes necessary to clean the debris from the rocks; otherwise, portions of the filter go anaerobic and begin to produce harmful things. If this were not true, why would aquarium stores sell all kind of devices to clean under-gravel filters?

    Oh yes, before I forget it, another consideration exists for liner ponds. If you have high ground water, it can lift the liner! Typical swimming pools are often required to have a pressure relief valve installed in the bottom. This is because such pools are often empty for various reasons, and water pressure from underneath can lift even a concrete pool. In fact, I have seen a filled swimming pool that was lifted about a foot and had to be demolished! The relief valve should have allowed ground water to flow into the pool and relieve the excessive pressure, but it failed. If a liner pond is installed in a region of fairly high ground water, a lot of heavy rocks on the bottom may hold the liner in place. Note, however, this is not for aesthetics but to provide enough weight to counteract the groundwater pressure.

    Now the choice is up to you. Is the aesthetics of rocks in the pond more important than the possible complications introduced? Finally, one other consideration is something called the stocking level. No, not something related to the stockings you wear on your feet, but the quantity of stock (koi) you run in your pond. If you really want a natural pond or stream, you might notice that no natural system carries so much stock per unit volume.

    Note - From Aqua Art: This photo shows algae feeding on detritus that is collecting in dead zones created by loose rock. This organic debris builds up and is decayed by undesireable anaerobic bacterial action, which, among other by-products produces hydrogen sulfide. Anaerobic bacterial growth is the type of bacteria used in septic tanks. Pond systems should always strive for environments that encourage aerobic bacteria colonies such as amended rich top soil in a healthy garden - a sweet earthy smell."

  3. jd boy

    jd boy LawnSite Member
    from nw ohio
    Posts: 179


    very interesting article I think you are more into koi and koi ponds than most of the rest of us. I bet a lot of people didn't know the difference. You have seen pictures of my ponds, and I make the conscious choice to have stone and gravel because of the aesthetics. To me, the benefit of how awesome it looks out weighs the negative of having to do a good cleaning every year.
    I think you just need to be aware of that fact before you build.

    Also, I have always been afraid to put one in, but wouldn't a series of bottom drains solve a lot of this stagnation issue?

    DUSTYCEDAR LawnSite Fanatic
    from PA
    Posts: 5,137

    i did an aquascape pond in my yard with lots of rocks and gravel and i have to say its a pain in the azz to clean and now that it is full of fish and i dont have a good place to put them to clean the pond its gettin dirty???????????
    the rocks looked great when i built it and everyone loved it but now that i have to matain it i hate the rocks so i am now stuck with a large hole full of water and rock that is full of fish i dont want to displace but am going to have to do something to clean it soon what fun
  5. drsogr

    drsogr LawnSite Bronze Member
    Posts: 1,275

    put them in a little kids swimming pool when you clean the tank.
  6. Victor

    Victor LawnSite Bronze Member
    Posts: 1,637

    Hi JD. You said that the aesthetics of the ponds you build, are more important to you, than the extra maintenance that will be required. The main thing I want to stress here, is that when a customer hires you to build a pond. You're not building your pond. Your building their pond. If the pond reqiuires extra maintenance, you're not going to suffer as a result from it. They're going to suffer from it. So the importance you place on aesthetics, compared to increased maintenance doesn't matter unless you're the one who will be responsible for the pond's upkeep. Since most customers don't know nearly enough about ponds to make an informed decision on this. I personally wouldn't build a pond that way. Joe wasn't just talking about koi ponds. He was talking about all ponds.

    I've definitely seen those beautiful ponds you've posted pictures of on here Buddy. I really like the way they look, as I'm sure your customers do too. The only problem is that (like I said before) most customers that approach you, wanting you to construct a pond for them, don't know a thing about ponds. That's why for the most part, I believe in saving them, from themselves (and their lack of knowledge). Most of these customers will tell you when asked about priorities, that aesthetics of the pond they want you to build for them, is a more important consideration, than how much more maintenance they will have to do as a result of having all of that pretty gravel lining their pond (at least that's what they will tell you before they get a taste of how much more work they'll have to do to properly maintain the pond you build for them). I equate it to that beautiful new car and the monthly car payment that comes along with it. When you're in the dealership's showroom, slobbering over that pretty, new car. You think to yourself that the payments won't be that bad. "If I can have this car, having to come up with that big monthly payment won't be so bad." But, once the newness and novelty wears off, that payment can start to become a pain in the butt! The same goes for a new pond and the maintenance that goes along with it. If you don't believe what I'm saying here. See DustyCedar's post about the pond he built and how he feels now about gravel in ponds. DustyCedar... I really feel for you Buddy. That can't be fun.

    When a customer pays you to build a pond for them, they're not just paying you to build them a pond. They're also paying you to build a pond that won't have design flaws built into it that will increase the amount of upkeep it will require to keep it in a healthy state of operation. Having said that. If a customer if dead set on having a gravel bottom in their pond and you warn them about all of the extra work they will have to do to keep it clean and they still have to have a gravel bottom, then at least they're getting what they want I guess. This doesn't just go for koi ponds. That goes for any type of fish pond. Like Joe said. Even in a watergarden. Having a gravel bottom will lead to cess-pool conditions if the owner doesn't keep up with the increased maintenance required.

    To answer your question about bottom drains. If you're going to have a gravel bottom on your pond, you're wasting money and time installing bottom drains in the pond. Gravel on the pond floor will impede (if not totally stop) the progress of detrius toward the drains. Just like putting gravel in your bathroom sink would affect the ability of draining water to draw hair and other objects toward the drain.

  7. jd boy

    jd boy LawnSite Member
    from nw ohio
    Posts: 179


    i totally get your point, and i agree that the aquascape approach (basically that is what we are talking about) has its flaws. I always try to accurately convey the maint. requirements that go into keeping these ponds clean.

    The vast majority of our customers just have us do the spring clean out. Really that is the only extra maint. involved. Throughout the growing season it is no problem to keep water conditions clean and in acceptable levels.

    And again I always convey to my customers, to me the natrual rock is worth doing 1 good clean out / year.

    I kinda thought the gravel would negate the usefullness of a bottom drain.
  8. jd boy

    jd boy LawnSite Member
    from nw ohio
    Posts: 179


    don't get me wrong, i'm not picking a fight. quite the opposite, i enjoy discussing these issues with you
  9. Victor

    Victor LawnSite Bronze Member
    Posts: 1,637

    There was nothing to take offense to Buddy. I've got to tell you. You make really good looking ponds and you obviously are up front with your customers about the maintenance issue. Keep cranking out those beautiful ponds! I'm looking forward to seeing more pictures this summer.


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