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Thread: Pulsed flow

  1. #21
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    I don't think so, at least not IMO. The purpose is not to stop and start the flow as it is to reverse the flow direction, or increase the flow dramatically. For the latter, it might work to have a secondary pump that is cycled on and off, but this would not account for the directional reversing.

    What about a combination of the waterfall standard slot pipe and a spray bar like acorral uses on his scrubbers, except more randomized hole placement, then one could turn that spray bar pump on and off to break up the growth pattern? I'm thinking of something funny now, our kids have a sprinkler that they play in that has a bunch of rubber hose sections that flail back and forth...like this http://www.sears.com/sports-and-toys..._tnt=39869:4:0

  2. #22
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    I am sure I have not read every thread since I have been away but, just my 2 cents.
    My horizontal scrubber in my pod tank has always been a semi floating deal (half of the horizontal ramp is in the water) but I never thought anyone would build one. Floyd calls it the blob LOL. It works better then a horizontal that is out of the water but surely falls short of a water fall type.
    Kerry
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  3. #23

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    I think this is a good idea but, instead of thinking around a horizontal screen, I think it would be better to evolve around a vertical screen. Something like...

    - Screen sits inside chamber with an inch clearance from both faces, the chamber has a bottom feed in on one end and similar feed out on the other. How you supply the feed in and dump it out is what needs a bit of thought.

    This may have already been mentioned but I've not scrutinised this thread

  4. #24
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    I have a freshwater system and I put together a small CSS algae scrubber. The water feeds in via my overflow and once it fills almost to the top with water the water is then surged out rapidly. It also has an air pump on it running bubbles along the screen. I made it so the bubbles could run across the front of the screen or the back of it. Right now I have it the bubbles running along the back side until I come up with a way to hide the air-holes so they don't get filled with algae.

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    It works like a charm but it does produce a lot of bubbles when it surges into the sump. I have reduced that by placing a cup underneath the output pipe and covered the top of it with screen material. The majority of the bubbles get broken up by the screen and dissipate along the surface.

    It fills up to about 80% allowing the water to completely cover the algae screen. I figure it is only filling about a half a gallons worth of water, so it doesn't affect the sump level too much. I don't use an ATO, but I could see where there would be a problem if I were to use a bigger container.

    Any thoughts on this build...pro's and cons?

  5. #25
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    I love it. That's exactly the idea I've been toying with. Now I know it can be made to work, ive got renewed confidence. What lighting you got on it, and what is the surge pipe made from, and what flow is going into it? The only things I would do different is make it double sided by having the surge pipe further away from the screen, make it thinner so theres only an inch or so of water between the screen and the container wall, and get the water to enter the container through a slot pipe that holds the screen so the screen has heavy flow when the surge is discharging and recharging. If I can get one of these to operate correctly I could get it to discharge onto my horizontal and provide exactly the surge that Adey suggests is required.

  6. #26
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    Great design cdm2012! Only issue I see which you already mentioned, is using it with an ATO on the system.

  7. #27
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    I think what it all comes down to is this: when is the filter filtering?

    The answer is: when the water is moving across the substrate.

    This is the crux of all algal filtration systems.

    For the horizontal scrubber, dump-style, it filters when the water rushing past the screen. So when the tray is filling up, there is some filtering as the water is in the process of submerging the growth, but it isn't until the dump happens that the water is rushing past it. Recent discussions about the efficiency of horizontal scrubbers (here and on RC, an a few references on Inland Aquatics' site) have brought up the supposed fact that true turf algae has a nutrient fixing ability 10 to 100 times that of other photosynthetic organisms, including GHA. I haven't looked into turf much and ashamedly haven't read Dynamic Aquaria, so with that being said, the fact that the vertical scrubber always has water running across it makes it a different system...

    For the vertical scrubber, waterfall type, this is under constant flow.

    For the upflow scrubber, the bubbles provide the motion for randomness but the water flow is low, which is IMO it's downfall. Could be the same problem for the floater, but I'll wait until the marketing hype is over and we actually see the product.

    But, back to the OT, I think that the issue (potentially) with yours is that it is only filtering when the screen is underwater and the bubbles are causing the random motion. When it is surging out, there is some motion there as well, but it's not really surging past the algae as it is draining off of it.

    I'm not saying that it's not working - it obviously is!! The "pro" might be that there is a benefit in the fill/drain/repeat process that keeps the algae changing positions and does not allow for air pockets to stay formed. On my UAS, once the bubble bar gets clogged (only a few days in) then the screen is covered in air bubbles, it looks like little eyes everywhere - kinda creepy actually.

    I think that the ideal combination of a surge and waterfall would be a CSS that dumps into the bottom of a waterfall chamber. I think of one of my L series scrubbers with a third drain on one side, so that the scrubber is normally operating as any waterfall scrubber would, but then the CSS would surge and fill the box up completely, and then the emergency/secondary drain would purge out the surge. This would have the effect of temporarily filling the box and breaking up any structure that would form and trap air or mat over growth, etc. The period between surges could be rather long, as it is not really necessary for the filtration to be effective - rather, it would be just a means of performing a secondary function of breaking up the "monotony" of a constant waterfall flow.

    EDIT: I seem to be repeating myself...for anyone reading this entire thread...sorry!! I said this all once already!

  8. #28
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    Thanks Garf. Build info: The screen is 3.5"X7.5" (roughly 26 sq in). I feed 1 cube of food a day.

    My lighting right now is a 23w cfl. But I want to change to LED's or an LED bulb in the near future.

    Right now my flow into the scrubber is close to 120 gallons an hour.

    It takes about 15 seconds for the unit to fill and about 6 seconds to surge out.

    The Carlson is made out of 1 inch PVC.

  9. #29
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    Thanks Ace! And thanks for the comments Floyd!

    Floyd, you mentioned that the only time the filter is filtering is when water is moving across the substrate. Does it have to be moving rapidly? When the filter is draining, water still remains on the screen, albeit it is a thin layer of water, but it is not dry. In fact, you can still see water slowly draining downwards due to gravity until it refills (which it does rather quickly). I'm assuming that it is still doing some filtering and in addition, I believe exposing it to the air might allow the algae to encounter some CO2.

  10. #30
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    I would be talking out of my rear if I said that air exposure did or did not affect CO2 uptake of algae, so I guess I can't really answer that one...someone else might know.

    I would venture to throw out an educated guess that even though there is some water still draining off the screen as the CSS drain the box, the effective filtration would be a function of the rate of flow, so as less and less water is actually clinging on to the screen in the process of draining, the effective filtration would drop at a rate that was close to the amount of water left on the screen. I would think that would probably be something that is close to impossible to actually measure, even with good scientific equipment, because we're talking about a snapshot in time of the primary production process.

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