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Problematic Planted Tank, Why is it not Growing faster ?

Discussion in 'General Plant Topics' started by Rovik, Feb 2, 2013.

  1. Rovik

    Rovik Junior Poster

    Jan 22, 2012
    Likes Received:
    Local Time:
    10:19 AM
    Hey Barr Report,

    Let me cut the the chase, I have a 5'x2'x32" aquarium holding approximately 700L.
    My Specs are as follows:

    Lighting: 3x 125W HQI (High Pressure Mercury vapor) Downlights (12 hour photoperiod)
    Filtration: 2x EHEIM Pro 3 600
    CO2: Milwaukee Controller + Regulator (Splitter regulator, An atomizer running on each cannister for even diffusion)
    Substrate: 2 inches of Aquasoil capped off with 2 inches of inert Black gravel.


    18W UV (Inline)
    1x Hydor 300w heater

    Water Sample as Follows:

    K - 20ppm
    CO2 - 80ppm (La Motte Titration)
    KH - 6.5'
    GH - 10'
    Ca - 40ppm
    Mg - 20ppm
    PO4 < 0.05ppm
    Fe - 0.5ppm
    NO3 - 15ppm


    When I first set up the aquarium, Everything was all well, The plants frequently pearled and growth was at a fast level that Id expect.
    Slowly the aquarium went downhill and the scape's growth halted. Mainly due to the fact that I got lazy and slacked off on water changes and dosing.
    I did a rescape with a new layout and once again began testing Elements and adding as I needed them on a proactive basis.

    For my effort I was rewarded a brief period of pearling but now has diminished once again to poor growth For whatever reason.

    I water change once weekly 50% or more, Dose API leaf zone according to the bottle, KNO3...GH(Mix of K,C,Mg salts).

    Now correct me if I'm wrong, But I am led to believe some plants e.g. Certain (for example) Aponogetons among many others have large surface areas and adaptations to cope with nutrient deficient waters in which they live and as such, When they are supplied with excessive amounts of phosphate in Particular (say >0.5ppm) Growth becomes irregular and appears as Holes in the leaf, poor growth ect. The idea is that some plants cannot regulate Their phosphate intake and as such cause's "Hick up" in cellular/metabolic reactions.

    I have been told also that some plants for example stems are subject to conditions with reasonable phosphate levels and therefore do much better as they grow faster and need the phosphate on a regular basis if maximum growth is to be achieved. (Liebigs law)

    So on trouble shooting this issue previously I places lanthanum based "Phos-out" pads in my filter. I did however notice my Nuphar Japonica which died off previously (Apparently from high phosphates) come back from the Rhizome after my the phosphate pads had removed bulk of the phosphate. Mere Coincidence ?

    And I am having no issues with algae, Only growth.
    (Perhaps only mild algae on the plants that are not growing)


    So finally, I would like some insight into what people think is limiting growth ?
    What should be changed or corrected, am I correct to hold the above Statements as correct ? Is there any documented study's on phosphates Reducing growth.

    Here is the link to my tank journal if you would like some more information:

  2. Tom Barr

    Tom Barr Founder
    Staff Member Administrator

    Jan 23, 2005
    Likes Received:
    Local Time:
    10:19 AM
    Are you a member of Aquaticlife Forums in OZ?
    There are a few that can help you and a few from Perth area. Most obviously from the East.

    I have kept many Aponogetons and have a large Lace plant in my 180 that will not die.
    I add 5ppm, 3x a week to that tank, it grows all plants, mini butterfly, Lace, Rotala sunset, Neaseas without any issues.
    I add 15 ppm 3x a week of NO3.

    My CO2 is a verified and referenced against a known standard at about 70ppm.
    O2 is 7-9 ppm depending on time of day.

    My KH, is 20 ppm or a little over 1 degree, and the pH is roughly 5.8-5.9 with the CO2 on.

    Now the KH you have might be mostly non carbonate alkalinity.
    So you might think you have a lot, and with a KH of 6.5, there's room for that, with a KH of 1? No, that's mostly all carbonate.
    You could be off 2-3 degrees, but I can only be off by 1 degree at MOST.

    You are REALLY limiting the plants with such low PO4.
    All plants regulate the PO4 endogenously. The sediment has a lot higher PO4 than the water generally.

    But I've found zero evidence to support high PO4 causes algae or harms plant growth in any way.
    400 plant species and types later later............I think I've done enough homework to make statements to this effect.

    You can try this also if you honestly believe PO4 are bad: pulse dosing. You dose 0.2ppm PO4 2-3x a week and watch the growth, do this in the morning, then watch the tank later in the day.
    You should see rapid pearling and dramatic growth differences.

    Adding all the CO2/light, NO3 etc will not help if the PO4 is the rate limiting step/nutrient.
    Also, ADA aqua soil is loaded with PO4.
    So roots can access it, but adding it to the water will still produce dramatic differences.
    See the aquascaping section here and view my tanks, they all have 100X more PO4 than your tank does.

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