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Thread: Fluidized media bed in 55 gallon sump.

  1. #1
    DIYFK member AZB's Avatar


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    Fluidized media bed in 55 gallon sump.

    I am setting up a 75 gallon tank, plumbed through a wall into a 55 gallon sump with a beananimal overflow. The original plan was to filter water from the dsiplay through filter socks and then through a DIY wet/dry bio tower, which would be fed by the return pump with a tee off the return line. I will most likely be keeping African cichlids in the tank, which are usually densely stocked and heavily filtered. I also will probably upgrade to a larger tank in a few years, something custom like 60"x30"x24", so I want to have room for growth in my filtration capacities.

    The other day I stumbled across some videos of fluidized/moving bed filters, using K1 and similar media. I found this very intriguing, as it seems like it would not only be self cleaning and efficient as it described to be, but it also increases the amount of water in the sump, maximizing the total volume of water in a system, rather than just having a few inches in the bottom of the sump.

    I am floating the idea of using 24 or 30 inches of my sump as a fluidized filter. I want to add a purigen reactor in the sump, so I will want some real estate in the sump to be open. With that kind of volume I think 2 cubic feet of media would cover me, with a little to spare. I get the impression this would be far more bio capacity than I would need, even with a heavily stocked cichlid tank, but I would be fine with that, knowing if I go bigger, the filtration can handle it.

    Any thoughts on this approach vs a wet dry tower?

    Thanks,
    AZ

  2. #2
    DIYFK member Nil13's Avatar


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    Well the MB requires aeration whereas the tower just requires gravity. Both need a mechanical stage before them. Remember that you need enough headspace in the sump that when the power goes off you have enough room to hold the water that will drain down from the display tank.

    I like MBs, you can set them up for plug flow pretty easily and don't have to worry about channeling that way. The towers are popular with koi guys but they use feather rock or cermedia instead of bioballs to get denitrification. But you need really good mechanical to do that.

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    DIYFK member AZB's Avatar


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    I will be using filter socks, probably 200 or 300 micron, for mechanical filtration. I did some calculations, and I will be looking at about .75 inches of rise in the sump from the display tank, and about .25 inches from the plumbing lines draining. So I'll make sure to have that, plus a healthy margin of error, available for when the pump isn't running.

    Doing a little reading, it looks like 1 cubic foot of K1 is a common and easy to obtain quantity and will be far more bio capacity than I would need, even if I upgrade the tank in the future. I am fine with this, but do have a question about the configuration of the bio chamber. With 1 cubic foot of K1, assuming a 60% fill ratio, I will need about a 14" long x 12" wide x 17" high chamber for fluidizing the media with 12" being the width of the 55 gallon, and 17" being how deep I plan to have the water in the chamber.

    Will a 14"LX12"WX17"H chamber fluidize easily, using two bubble wands near each end, as Joey has in his videos? Would I be better off going longer and getting more media? I am fine with using more space and paying a little more if the media will be easier to get into a good flow pattern. If it will work at the dimensions I have listed though, I think 1 cubic foot will be more than enough for any tank I could conceivably put in the space.

    Thank you,
    AZ

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    DIYFK member Nil13's Avatar


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    It sounds like you are thinking about it like a conventional sump filter with all those upflow and down flow chambers.
    You should think of it more like a plug flow trough filter. You build the sock filter like normal except you don't have all the water flowing under the baffle. Instead the baffle is a grid plate or matala mat that holds the K1 in place. Then do that to the other side. If you use mat it's adjustable.
    If you want something to look up as reference while I work on a little sketch, lookup ERIC trough filters for koi ponds.

  5. #5
    DIYFK member Nil13's Avatar


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    Ok so here's the basic idea. You create a way to suspend the socks on one end and you put a baffle on the other end to set the water height and create a pump box. Then in between, you can do whatever you want. So you put two screens to hold the K1 in there at the appropriate sizing. Before the first screen, you put a wand to mix the water and get the plug flow started. (It will also air scrub the screen) Then in the MB you just want to stir the bed. Could probably use one wand down the center instead of the two I drew. Coarse matala is easy because you can just squeeze it into place.Click here to enlarge

    Sent from my SAMSUNG-SM-G890A using Tapatalk

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    DIYFK member AZB's Avatar


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    Thank you Nil13,

    I was looking at plans using egg crate and needlepoint canvas, but that matala mat looks like a much easier solution.

    Would you recommend the coarse mat, which I typically see being green, or the very coarse, which is black?

    Does this type of filter produce micro bubbles, and would putting in a stepped baffle before the pump chamber be a good idea?

    Have a good one,
    AZ

  7. #7
    DIYFK member Nil13's Avatar


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    You are just trying to keep the K1 in place so the extra coarse would be fine. However, whichever is cheaper would be how I would decide. Lol

    All the bubbles have to get through the mat and then over the baffle. There shouldn't be too many micro bubbles. It's not like it's a protein skimmer on a reef tank. That said, baffles will always produce bubbles so a bubble guard on the output side like below would be useful. I don't think you would need both input side and output side bubble guards but if it works for a skimmer it'll work for a moving bed.Click here to enlarge

    Sent from my SAMSUNG-SM-G890A using Tapatalk

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    DIYFK member Nil13's Avatar


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    If you are worried about bubbles, you can also increase the size of the pump box. That will decrease the depth of your draw down and make bubbles more likely to get caught between the guards.

    Sent from my SAMSUNG-SM-G890A using Tapatalk

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