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Depth of Media in Biological Filtration Chamber

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  • Depth of Media in Biological Filtration Chamber

    Hi all,

    I've been a lurker for a long time but maybe its time to come out of my shell.

    For biological filtration using J-mat, Peter W recommended to go no deeper than 10 inches (or thereabouts) as its effect will be significantly compensated once the media is further submerged.

    My matting is currently 18cms submerged and I can definitely see healthy biofilm on the media at the bottom. I have also seen people with very high stocking using deep filtration chambers with excellent results.

    Trying to better understand where Mr W is coming from and if anyone has any experience with this?

    Thank you all!
  • #2

    Welcome! Too many lurkers never speak up. And that's a good question. I am not certain what all Waddy may have had in mind. I've learned that he often provides his bottom line advice without laying out all the reasons. I would expect his concern relates to maintaining high oxygen levels in the water being filtered, maximizing the nitrification process while minimizing the risk of potentially harmful heterotrophs being given a large homeland within the filter. If that is all that is behind the recommendation, then I'd say it is a rule of thumb that can be varied if the particular system is able to maintain adequate oxygen levels. Much will depend on flow rates, temperatures, etc. However, I am not sure if that is what he had in mind, or if there is more to it than that.

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    • #3

      Shaw,
      Welcome to the board! Glad you've decided to post.

      Most media hosts the thickest colonies nearest the source of air and food. In a down flow it's on the top of your media and on an upflow it's on the bottom.
      The kind of bacteria can also be affected by the natural UV present in light especially where the downflow is used.

      The deeper the media the more it affects the flow and the availability of food and air.To take advantage.

      I have 3 vortexes in series, 16 inch media, all up flow and all with an airpump for each individual vortex. I started with air stones on top to re-introduce air into the next chamber. I then , after 2 years switched the airstones underneath the media. The results were markedly better with the later. I thought all that heavy air would blow all the food and water by too fast.
      Don't know the theory but can tell you what works in practice. I'm not gonna change my system but if i was doing a new one I wouldn't hesitate to go ten inches for media depth. I've spent time with Peter and have an enormous respect for his knowledge. It's what he runs at his home pond. I know he's been working with EA and k-i but don't believe he's changed over yet or any time soon. BTW this concept came from Sakai-san of isawa. If you ever get a chance to read up on the man and his story you should do it.
      Dick Benbow

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      • #4

        Thanks for your insights.

        I do not have any scientific facts to back up my thoughts but my thinking is that unless there is good reason to suspect that the quality of biofilm for the entire media is compromised, then additional depth will provide more nitrification capabilities.

        As for gas exchange issues, this can be easily fixed with aeration - can't it?

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        • #5

          I do not think it is as simple as avoiding compromise to all the media. It also involves avoiding habitat for undesirables. Aeration should handle gas exchange issues .... trickle towers can be several feet of media and function wonderfully as long as the aeration is maintained.

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          • #6

            Thanks Mike for your input, good point.

            when k-1 first came out lots of folks under the theory of if a little bit is good a big bunch is better learned that it doesn't work in application. The constant stir of the air helped to expose the media to everything the bacteria needed and when too much was applied it didn't roil the same.
            Dick Benbow

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