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Thread: sand & gravel as a biofilter?

  1. #1
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    sand & gravel as a biofilter?

    People on a couple other forums keep insisting that a sand & gravel filter is not a good biofilter, yet here on Koiphen, the opposite statement goes unchallenged. The main argument against the SG as biofilter seems to be that when the filter is blown out, the bacteria will be stripped off the media. Is there anything to this idea? Or is there some other reason why an SG filter wouldn't make a good biofilter?

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    I don't have any proof for this, but I feel any time you violently disturb any media, sand/gravel or bead, you might be blowing off bacteria. I also believe with the S/G filter, the heavy gravel at the bottom that does not get disturbed will continue to hold bacteria.
    As an example, I have several tanks here, and a few small customer's ponds that run on S/G filters alone. We have never seen any ammonia spikes after blowing out the filter.

  3. #3
    ktran03 is offline
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    I was wondering this myself

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    Thanks Steve. Nothing beats reports from actual ponds.

    Do you think that a significant amount of the bacteria hangs on in the sand too? While I won't argue that no bacteria gets flushed out, it seems to me that between the sand having an irregular surface with protective recesses, the short duration of the blow out, and and the relatively low velocity of the fluidized media (compared to sand blasting) that a fair amount of bacteria would remain in the filter. It's hard to see how just the bacteria on the gravel would be enough to avoid ammonia spikes.

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    BaitWrangler is offline
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    Evening Otter, et all,

    Of course there is no debate that whatever is inside your s/g is going to be greatly disturbed every time you blow it out. It's quite impossible not to remove some of the bacteria now matter how you clean the water correct? Bacteria you have to remember is alive and is one of the simplest organisms there is. From a biological stand point I don't see why they should not be able to recolonize very quickly. Additionally, with no knowledge all at of pond chemistry - just a good background in biology, I'd say that constantly growing new bacteria in your filter is much better than trying to maintain one gigantic colony for an extended duration.

    Please correct me if work. You all are much more experienced.

    Ed

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    You may have a point about "harvesting" the bacteria every week instead of running an old bacterias' home, Ed.

    If anyone is interested, there's more discussion and a less overwhelming DIY thread here:
    http://www.thepondforum.com/showthre...-gravel-filter.

  7. #7
    jeff reiter is offline
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    the biggest problem with all the advice swimming around out there in cyberspace is the flawed thinking that one size fits all or that my pond is better than your pond. the simple fact is that there are four different types of ponds with koi in them, and using someone else's idea of what is best won't make sense if your pond is not in the same category as theirs. for example, a champion show pond will probably never have a sand and gravel filter mainly because that type of pond requires a level of cleanliness and reliability that is extreme for the average guy. a show champion may have to live in that pond for eight years before it can compete and cannot suffer one disfiguring injury for over 3000 days. these ponds have from 1000 to 3000 gallons of water for each individual fish, and i saw one recently with a filtration system that looked like it belonged in the city treatment plant. in contrast we have a display pond aimed at the simple pleasure of lowering our blood pressure every night after work. i'm not the least bit interested in taking a fish to a show. My ratio is targeted at 200 gallons per fish, and i use a straightforward over and under 8 foot long concrete sedimentation filter with four chambers and k-1 moving bed, matala, and bioballs. if you are not planning to win the next Niigata Grand Champion trophy this year, a sand and gravel filter might do just fine so long as you know the pluses and minuses of that filter versus another style and can keep it clean and functioning.

    so when you hear someone rejecting the use of a sand and gravel filter on the internet, consider the source.

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    BaitWrangler is offline
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    Well said Jeff!!! Not only that - when you hear anything in life.... consider the source!

    I've read before of folks pulling their fish out of shows because of bumps and bruises that occur in the holding tanks, etc. To us normal kin we'd say "what that little scuff" but to the show Koi grower, a cracked fin or a bruise on the nose is like your only son comming home from school with a shiner on his eye.

    Ed

  9. #9
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    A sand/gravel filter in my thinking is just one part of the whole system. I consider them a mech/polishing filter. I like to use them with other filtration such as a shower or moving bed when ever possible.

  10. #10
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    I've run my pond on just the 2 s/g filters because my bio-wave was offline (almost 2 weeks) without any ammonia readings showing up.

  11. #11
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    Just a thought...
    Perhaps blowing out the S/G is much the same as what occurs in a MB. The old bacterial layers are sloughed away in favor of new, young, more vigorous, bacterial colonization. Instead of thinking of it as removing bacteria and making it a poor Bio filter, I believe that it's more likely in cleaning out the accumulated gunk you are also working towards maintaining healthy bacterial colonies.
    Cori ~Viva la Goldfish!~

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