Do we need a filter?

Discussion in 'General Planted Tank Discussions' started by Themuleous, 16 Jan 2008.

  1. Themuleous

    Themuleous Member

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    Location:
    Aston, Oxfordshire
    As some of you may know I recently experimented with growing HC emersed, but as it was not working I added some NH3 to the water I was spraying the plants with to see if that helped (it didn't BTW). I did a NH3 test on the water that was in the tank 24hr after it got a spray and the test showed no NH3. I can only assume this was either used by the plants or got converted to NO2 or NO3 by bacteria in the gravel (I didn't think to test for NO2, idiot).

    Anyway, now that I've flooded the tank, it got me to thinking, in a fully planted tank with a moderate fish load, is there any need to have a filter other than for mechanical filtration? I.e. the plants do all the NH3 and NO2 filtering for you? Similar to live rock in marine tanks? At the moment I just have a small power head pushing the water around the tank with no form of biological filter at all. Granted I have no fish but when I add them would there be a need to add a form of biological filter or would the plants take up the slack happily without it? I would still need to maintain the water movement around the tank.

    Just some Sam ramblings, if anyone has any views/thoughts?

    Sam

    PS - I've got a great CO2 set up. The diffuser is fixed below the powerhead (I say powerhead its just a standard internal head just with the sponge chamber removed) so the tiny bubbles get sucked into it and chopped up into even small bubbles (almost too small to see), these then get pushed around the tank. Diffusion has to be near 100% and the bubble rate is far lower than I've previously run on the tank. I'll get some pics up if people are interested.
     
  2. Dan Crawford

    Dan Crawford Founder Staff Member

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    3,266
    Location:
    Daventry, Northants
    It sounds bang on in principal and i can't see and issue really, i believe that in the substrate a lot of biological activity goes on ie. the breaking down of waste much like in "a gold fish bowl" so syphoning the substrate heavily may be a bit of a hinderance to the bacteria. Like you've mentioned, the plants play a vital role and given a high enough biomass and low stocking density in you relatively small tank i can't see any real problems.
    Get some fish, keep an eye on the water and lets see and experiment!
     
  3. Themuleous

    Themuleous Member

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    4,126
    Location:
    Aston, Oxfordshire
    Nice one, cheers Dan. Glad to know I'm not talking complete gibberish! I'll give the HC a few weeks to get going and grow a decent amount (although it was pearling yesterday, just one day after being flooded so thats a good sign) before I add the fish. But when I do, I'll monitor NH3 and NO2 in particular to see what happens.

    Sam
     
  4. SuperColey1

    SuperColey1 Member

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    2,668
    Location:
    Lincoln UK
    I think in theory you could run your filter empty just to keep the circulation good and spread the carbon/nutrient.

    This would of course then mean you could use smaller filter as the flow would not be so limited.

    The one good thing about keeping some media in though is as a backup in case of ammonia spikes.

    Andy
     
  5. Ray

    Ray Member

    Messages:
    474
    Location:
    Switzerland
    I run my 25L with a HOB filter that only has a fistful of ceramic noodles and a good sized pinch of filter wool but it does turn over 250L/hour. I have about 30 guppy fry sized 1 to 2cm and no problems. I think half a dozen fish would be fine...
     
  6. Keith

    Keith Member

    Messages:
    27
    Hi,

    Here is a picture of my 4' tank. It has been set up since 17th May last has no filter, just a power head for circulation, and has had no water changes.

    small201107.jpg
     
  7. Mr G

    Mr G Newly Registered

    Messages:
    7
    Location:
    Whitwick (Nr Leicester)
    Hi Sam,

    Although I've never used this method, it would certainly seem possible, Diana Walstad covers this method in her book "ECOLOGY of the
    PLANTED AQUARIUM". Although her book/method is biased towards low tech/natural tanks, i cant see why it wouldn't work on higher tech setups.

    I imagine much of it's success (or failure) would depend on the fish bio load and the plants used. I'd guess that fast growers would be a better option than the slow growing plants.


    Al
     
  8. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

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    8,937
    Location:
    Chicago, USA
    Non-biofiltration is not really a good idea on a high tech tank. Although both the low tech and high tech systems operate on the same principles they are each at the opposite ends of the spectrum. In a highly lit tank ammonia production is accelerated due to high metabolism. The consequence of ammonia in the presence of high light is algae inducement. Ammonia consumption by the plants is also higher but not high enough to preclude competition by algae. Biofiltration in a high tech tank is therefore critical because it allows the filters highly populated bacteria colony to consume the remaining levels of ammonia.

    In a low/moderately lit tank the ammonia production is lower and the metabolism is lower. Low light suppresses algae production and in this type of environment the presence of ammonia is less of an issue. A low tech tank therefore operate much more like a sewage treatment plant as it recycles organic waste with a much lower risk of algae. It is for this reason that inorganic dosing requirements are much lower. So, yes, low light, low growth, low filtration rate (low bacteria colony) all work together in this scenario.

    While it is true that evacuating the filter box will increase flow rates and provide better nutrient distribution, in a highly lit tank this benefit would be offset by higher levels of ammonia and consequently, higher risk of algae. From this standpoint organic waste is a killer in a high tech tank.

    By the way, this is also the main reason frequent and/or large water changes are recommended in high tech tanks - the control of organic waste (which leads to ammonia). Controlling nutrient buildup, as so many people believe, is actually a secondary concern since high nutrient levels are not the cause of algae 8)

    Cheers,
     
  9. George Farmer

    George Farmer Founder Staff Member

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    7,089
    Location:
    Cambridgeshire
    I'd stick an Eheim Pro 3 on there. :D
     
  10. Themuleous

    Themuleous Member

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    4,126
    Location:
    Aston, Oxfordshire
    Thanks people,

    Ceg - I don't quite follow, what in a high light tank is producing the extra NH3? The plants?

    George - thanks for that...
     
  11. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
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    Location:
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    Hi Sam,
    Mainly the plants, yes. High growth rates demand higher metabolism and produces higher waste products. If you eat more you grow more but you also produce more waste as well. You've also got increased levels of bacteria living and dying in the water, surfaces and soil as well. Anything that dies produces ammonia as it decays. I don't think it's as much that there is an inordinate amount of extra ammonia production but that whatever ammonia is produced, when combined with high light triggers algal blooms. Additionally, If CO2 is the least bit lacking for that lighting level the result will be deficiency and the plants will start ejecting organic products and ammonia back into the water column.

    One of the highest priorities in a high tech tank therefore is to eliminate as much as possible any source of ammonia. This includes biofiltration. This includes regular and persistent removal of anything dead or dying such as floating leaves, weak leaves, mulm or detritus on the substrate surface or filter. This includes regular water changes to lower the ammonia concentration (and to remove algal spores). This also includes making sure that circulation is maxed out by virtue of strong pumping capacity, and that CO2 injection is as close as possible to "unlimited" levels. Strong circulation does two good things; it keeps particles suspended longer, increasing the chances that the particle will be sucked into the intake, and it helps to deliver nutrient /CO2 laden water to the leaf surface. It also goes without saying that proper nutrient levels to avoid deficiency and subsequent organic product leaching across the leaf surface is important.

    Cheers,
     
  12. George Farmer

    George Farmer Founder Staff Member

    Messages:
    7,089
    Location:
    Cambridgeshire
    Well put, Clive.

    It also explains why Purigen can be helpful in preventing/treating algae, as it removes organic nutrients like NH3/4.
     
  13. Themuleous

    Themuleous Member

    Messages:
    4,126
    Location:
    Aston, Oxfordshire
    Better fish out the old 2211 then...
     
  14. Dave Spencer

    Dave Spencer Member

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    1,389
    Location:
    N. Wales
    Interesting stuff as always Clive.

    I must admit, though, I wasn`t aware that ammonia was one of the leachates from healthy plants. Ammonia leaching from unhealthy plants is an algae trigger, and occurs at more elevated levels I would imagine, but considering the low levels of nutrients in which algae can thrive, does this not imply potential algae on plants that are 100% healthy?

    I know one or two people with perfectly executed tanks still struggle from algae on healthy plants such as Anubias sp. I wonder of the ammonia levels leached from this plant, as an example, creates a good environment for localised algae growth.

    Perhaps this is why it is recommended that the plant is kept in shaded areas. Less light =less growth = less ammonia leaching out = less algae.

    Dave.
     
  15. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,937
    Location:
    Chicago, USA
    Hi Dave,
    Just to clarify, I wasn't implying that healthy plants leach ammonia, but that growing plants always have bits and pieces that are ejected or wither as a normal consequence of growth. The normal metabolic products that are ejected from healthy plants I believe are the complex organic molecules such as proteins etc. which then subsequently break down and forms ammonia.

    Anubias is notorious for getting algae even though it appears healthy but I see some leaves of my fast growing Alternanthera sometimes getting algae as well, even though the plant overall is robust. High light simply exerts tremendous growth pressures on a plant and perhaps, if an individual leaf is in a less than perfect position, it doesn't get it's proper share of nutrients/CO2, then falters, and is then attacked.

    Cheers,
     

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