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Thread: How to calculate filtration system?

  1. #1
    Sansai Reza's Avatar
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    How to calculate filtration system?

    Dears,

    Dose any one could help to know more about how to calculate filtration system such as volume, circulation, required QTY of medias?

    Regards
    Reza
    KoiRun likes this.

  2. #2
    Daihonmei MikeM's Avatar
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    I have seen a lot of general guidelines suggested over the years, but they vary greatly. It is sort of like the question 'How many gallons should a koi pond be?" Having adequate filtration requires consideration of the stocking level, the size of the fish (or pounds of fish), the amount of feed and pond volume. The Japanese breeders have very dense stocking levels in their greenhouse ponds over winter with comparatively light filtration, but they are not feeding much of anything for 5 months and often have a continuous trickle of freshwater entering the pond. Ramp up the feeding to get strong growth, and the filtration would be grossly inadequate.

    For a long time it was generally stated that the flow rate through the filter(s) should equal half the gallonage of the pond per hour. In other words, the pond volume would 'turnover' every two hours. I still see this stated, but nowadays it is usually given as a minimum. I think most koikeepers end up trying to have the pond volume turnover every hour or a little less. (My pond is about every 45 minutes.) A two-hour turnover rate works, particularly with a lightly stocked pond. As stocking per gallon increases, turnover needs to increase.

    The volume of water in the filter system is only important in relation to the type of filtration. Prior to use of bead filters, moving bed bio-filters and shower filters, when filter systems were mainly slow moving water going through a series of settlement chambers, brushes and mats, it was said the filter should be about one-third the size of the pond with about 20-30% of the total system gallonage being in the filter. Advancements in filtration have allowed much smaller footprints for filters. A 4-tray Bakki Shower type filter with effective mechanical pre-filtration can easily handle 5,000 gallons per hour using Bacteria House or similar ceramic media and will contain only nominal gallonage of flowing water at any particular moment.

    Likewise, the quantity of media depends on the type of media and the type of filter. The efficiency of K-1 Kaldnes type media is greater in a moving bed filter than when used in a static application. The exposed surface area of the particular media suitable for bio-film development is the important factor for comparison. Bio-balls have less surface area for a particular volume than K-1.

    The low-tech slow flowing filters from the 1980s work fine and are inexpensive to operate once built. If space is not an issue, they are practical.... and still the most seen at Japanese breeders' farms. For hobbyists, space is usually an issue and most folks do not want to spend anymore time on filter cleaning/maintenance than they must, so we end up with fairly complex systems with lots of pumps and plumbing that cost more to install and use considerable electricity. Then folks look into ways to decrease operating costs, like using aeration to move water rather than pumps.

    So, in the end, I think a person has to decide what type of filter they want given their space limitations, budget limitations, time limitations and their climate. If I was building my pond from scratch today, in my warm climate, I would use gravity flow to screen filter for mechanical, followed by settlement chamber with a mat to capture most of what slipped through the screen stage, and then pump to shower filters. My goal would be to move about 17,500-20,000 gallons per hour (12,500 gallon pond) through the shower filters. Everything would be sized to allow that volume of flow.
    Last edited by MikeM; 08-25-2016 at 12:38 PM.

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    Oyagoi yerrag's Avatar
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    Interesting Mike that you would still have a settlement chamber after the screen filter, which I take to be a sieve or a drum filter. This implies fines finer than 40-60 microns would still be a significant amount, enough to affect the operation of the shower filters over time. I was thinking if a poly wool filter across the cross section of the chamber would do the job. The poly wool could either be disposable or be cleaned and reused, depending on the pond keeper's environmental consciousness.

  4. #4
    Daihonmei MikeM's Avatar
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    The important point, Yerrag, based on my experience in my climate, is to minimize to the greatest extent practical the amount of solids reaching the shower filter. A quite large settlement chamber would work for what I have imagined and would be simple to maintain daily. But, settlement chambers only work for capturing fine solids if the water is very slow moving in the chamber. A lot of folks obtain poor performance from settlement chambers because the water flow is too much to allow gravity to do its job. An alternative taking much less space would be a static kaldnes chamber with aeration for cleaning. I currently use mats in the top tray of my Bakki to capture debris before it reaches the Bacteria House media. This has significantly reduced the amount of gunk captured in the media, but has not eliminated it. Stuff still gets through and builds up over time. I have an annual practice of removing all of the BH, swishing each piece in a bowl of water (dechlorinated, of course) to remove accumulated gunk. I should probably do it quarterly, but it is a tedious chore with a lot of bending. Doing it annually has been good enough. Perhaps if I had a screen/sieve pre-filter this task would not be needed. However, as good as screen/sieve filters are, my observation has been that stuff makes its way through. Even a tiny bit mounts up over the course of a year... and all the finer media will capture it. A shower filter with a more open media, like the larger bio-balls, does not hold much debris, but also does not have as much surface area. There are always trade-offs.

  5. #5
    Oyagoi yerrag's Avatar
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    "However, as good as screen/sieve filters are, my observation has been that stuff makes its way through. Even a tiny bit mounts up over the course of a year... and all the finer media will capture it."

    40 microns is still 40 microns, even if it is the finest a drum filter would be designed to filter. My dealer told me once that he has clients using polywool to filter their ponds. I didn't think it was a good idea, knowing that his clients weren't using sieves or rdf's. There would be too much work keeping up with replacing or cleaning the polywool. But if what's to be filtered were fines that are smaller than 40 microns, I would consider it.

    I haven't installed the used rdf I got because it still is difficult to do any mods on an existing pond, but I have a static k1 filter, and a 2 meter long x 60cm wide x 60 cm "raceway," and I think if I put a polywool filter with the 60 cm x 60 cm area (cross sectional area of the chamber at the end, it would be manageable. Replacing it once a day isn't ideal, but if I had an rdf instead, I may only replace once a week. It makes sense to have a settlement chamber after the k1 filter, but as you said, it is as effective as the size of the settlement chamber dictates, the larger the better. But like you, I wouldn't find a vortex design practical. I would instead opt for a radial flow design.

  6. #6
    Oyagoi yerrag's Avatar
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    I didn't design my filter, so I really couldn't say with confidence how I would calculate the filtration capacity. Since most people are just fortunate to build a koi pond once, the thought of building a better pond from his first pond "mistake" is out of the question. And it is difficult to build a pond that is perfect from the get-go, since there are many designs out there, and most opinions are based on the adviser's limited experience with his one pond and filter design. When one goes into building a pond, one has a budget. A "perfect pond" may be built for that budget, assuming you got it built right. As one grows with the hobby, he may find that the perfect pond isn't that perfect anymore. He will want to improve the water quality, and he will want to improve the filtering capability. He may find the need to do it as his koi collection expands, or because his koi are growing well that he needs to anticipate their future needs. He may also want to make koi keeping a more enjoyable hobby, and he doesn't want whole days off his wekend spent only on cleaning his koi pond. He's willing to spend more on improving his filter so he can have time for other things.

    This means your filtration design has to be such that it would be easy to modify in the future. It means that you have of to think of each filtration stage as modular, and that there would be "hooks" or interfaces that would join one module to another. Thinking of it this way, you would think of connections to these modules as connections that can easily be detached and reattached. Since at least somes of these modules would be automated, it would be practical to build in access for cables, even if there is none envisioned in the original design. Especially if the filter is made of concrete. Even a multi-chamber design, made of concrete, can be made with the thought of modularity in mind.

    This way, the filter can evolve as the keeper sees fit as he becomes acquainted with the different mechanical and biological filtration methods available. As advanced as we are at this stage, compared to 10-50 years ago, we can't help but think of ourselves as dated a decade or two later. I was bragging about having snagged a used rdf at ebay for a good price, only to have it sitting for nearing two years already, while a friend just a week ago told me he ordered a Blue Eco rdf from China. Now, he is bragging about an rdf that does not use any electricity, nor sensors, for a price more reasonable and affordable than what it was in the recent past - and I had to keep myself from betraying my envy;

    It would be nice to be always at the cutting edge of fitration technology, and not be constrained by the "this is it and I'll be fine" finality of the original design.

  7. #7
    Daihonmei MikeM's Avatar
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    At the time my current pond was built, there was no reason to think that I would ever consider using just shower filters, so all returns are comparatively narrow pipe intended for water to be pumped into the pond, except the one Bakki shower has two 4-inch returns for gravity flow into the pond. I cannot convert to all shower filters without re-plumbing entirely, and that is both an expense and massive disruption of the garden I'll not ever go through. Some things you just have to live with.

  8. #8
    Oyagoi yerrag's Avatar
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    When my pond was about to be built, it was designed with the main pump return plumbing at 1 1/4". It seemed fine and it would have worked. But right before I had the material list drawn up, the foreman whose real expertuse is with building waterfalls suggested that I increase it to 1 1/2". Since pvc piping is so affordable, I agreed with him. This was for the section of the return piping that goes thru the ground and back to the tangential pond return ( tpr), which was to be the main return line. I have another section of piping that goes to the 3-ft high waterfalls, and I decided to increase the size of the pipe from 1 1/4" to 2". In retrospect, I was glad I made those changes. The less friction in the pump return piping, with the larger size, the better it would be for the flowrate. It gives some leeway also for future increase in flowrate. I just increased the flowrate of my 5000 gal pond from 2500 to 3400 gph the other day by changing the low-flow impeller to the high-flow impeller of my Sequel Kohaku pump. I was having trouble with algae in the water, and with a persistent low reading of ammonia, and I'm glad I made the change. It cleared up the water in just a day, and the ammonia became more manageable. I guess no matter how I tweak my pond, my growing koi will just have to respirate that much ammonia no matter what, and the increased flowrate increased the bio filtration capability correspondingly, and it solved my problem. Now I can see why MCA bought his Flow Friend. I can appreciate much more having a variable flow pump that just works by the turn of a knob, and is right there when you need it.

    While it makes a lot of sense to overbuild the pumped pond return plumbing , I must caution any pond builder not to overbuild the gravity-flow bottom drain plumbing that goes from the pond to the filter. Too large plumbing will cause water velocity to be too slow that plenty of debri will find it to easy to settle into the plumbing. I have a neighbor with such a problem. Even after I pointed it out to him, he still doesn't flush his bottom drain more often to dislodge the debri. In fact, he continues to ignore flushing the bottom drain regularly. His koi doesn't look nice, and doesn't have the hearty appetite I see in my koi. That may be one major reason.

  9. #9
    Oyagoi yerrag's Avatar
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    Quote Originally Posted by MikeM View Post
    At the time my current pond was built, there was no reason to think that I would ever consider using just shower filters, so all returns are comparatively narrow pipe intended for water to be pumped into the pond, except the one Bakki shower has two 4-inch returns for gravity flow into the pond. I cannot convert to all shower filters without re-plumbing entirely, and that is both an expense and massive disruption of the garden I'll not ever go through. Some things you just have to live with.
    Ya, we make do and try to be creative!

  10. #10
    Sansai Reza's Avatar
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    Thanks to mike and yerrag for interesting writings. I think filtration system installation is vary to folk's knowledge, experiences, infrastructure and facility accessibility and of course money is biggest challenge. Koi keeping hobby is a gradual increase knowledge and experiences. Also is related to person's manner and style, I love water flows sounds that made by waterfall and bakki showers but my brother cannot rest by this sound and cannot tolerate such these sounds.

    As Mike said and I understand, filtration systems had to be related to many factors, amount of foods, count of fish, space water change periods and so on. I think that, almost there is no all-in-one filter to have all cons of filtration systems and no pros. I mean there is no Ideal filtration system to cover all kind of peoples all kind of needs and requirements.
    I did my self my pond filter. This pond has no bottom drains and it is hard to correct it that was poorly designed for pool. I used water pumps to run water through the filter, so I exactly understand what micron scale waste is because everything when pass via pump will be powdered. After several months testing filters I designed a filter with down up water flows barrel filter. I used thick and dense sponges, rock gravels and in the final stage I used Activated Carbon for removing water color and odor.
    This filter is very good but maintaining is very hard. I when I think to make next filter horizontal I found that space is other issue with this Idea.

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