This site is supported by the advertisements on it, please disable your AdBlocker so we can continue to provide you with the quality content you expect.
  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Where are my nitrates going?

Discussion in 'CO2 Enrichment' started by Carissa, Oct 10, 2007.

  1. Carissa

    Carissa Guru Class Expert

    Joined:
    Jun 8, 2007
    Messages:
    678
    Likes Received:
    0
    Recently I started testing nitrates (after my hygro started developing "burn" holes and dying off). My kit isn't 100% accurate but it does at least do one thing for sure, it tells me whether there is ANY nitrate in the water or not. Anyway, in my 32g non-co2 tank, I can add 1/4 tsp of KNO3 and two days later register 0 nitrates. That's with a full fish load too. What's up with this? Are the nitrates really being used up that fast in a non-co2 tank? Will plants take in nitrate faster if they are starved of it?
     
  2. Craig1970

    Craig1970 Junior Poster

    Joined:
    Oct 11, 2007
    Messages:
    1
    Likes Received:
    0
    If the "burn" holes are on older leaves, it sounds like K deficiency. What I'm wondering is, if your plants need K, will they take up the entire KNO3 molecule, use the K and store the NO3 or will they use the K and leave the NO3 if they don't need it?
     
  3. VaughnH

    VaughnH Lifetime Charter Member
    Lifetime Member

    Joined:
    Jan 24, 2005
    Messages:
    2,913
    Likes Received:
    44
    When salts dissolve in water they exist not as molecules, but as free ions, so KNO3 would be K+ and NO3- ions. That tells me the plants can take either or both ions as they need them.
     
  4. Carissa

    Carissa Guru Class Expert

    Joined:
    Jun 8, 2007
    Messages:
    678
    Likes Received:
    0
    Ok. I tried adding 1/2 tsp of KNO3 and after two days I was still showing nitrates, but maybe I'll bump up K by itself and see if the holes improve. Tom said it was co2 deficiency, which makes some sense because I stopped doing diy co2 around the same time that I started noticing the holes; but after four weeks I'm still getting holes in leaves and I would think that the plants would have adapted by now to the lower co2. Also at the same time I discontinued co2, I cut back to 1/3 my regular fertilizer dosage, which perhaps simply wasn't enough and compounded the low co2 issue.
     
  5. ceg4048

    ceg4048 Lifetime Charter Member
    Lifetime Member

    Joined:
    Mar 21, 2005
    Messages:
    240
    Likes Received:
    0
    Hi,
    Plants aren't concerned about low CO2 if there is low light. You mentioned that you discontinued CO2 and reduced nutrients but did you also reduce the light? If so, to what level. If not reduced sufficiently then they are still being driven to uptake CO2 and nutrients and are failing as a result. Additionally, if you are adding sufficient KNO3 and KH2PO4 for their N and P content then you are automatically adding enough K.

    Isn't it weird how one day your nitrate test kit returns a zero reading and another day it returns a non-zero reading? At some point one has to realize that NO3/PO4 test kits merrily lead you down the primrose path. First it tells you that you need nitrate so you add nitrate. Then it tells you there's enough nitrate so you add something else. The next step in the illusion is to rationalize or justify why it read low one day and read OK the next.

    I'm guessing that you have too much light. This drives a certain CO2 uptake which can't be met by ambient conditions alone. I have empirical evidence that you ought to be able to shut off the lights and leave them off, with the tank only receiving subdued ambient lighting and that the plants would recover more quickly. This sounds absurd, I know, but here is my evidence:

    Below is my "nutrient deprivation chamber". This is where I throw clippings, algae victims and other unwanted cast-offs. The basin is in the laundry room barely lit by a side window. These victims stay in the sink until someone else wants them or until they rot, whichever comes first. There's very little CO2, no nutrients except what's in the tap (or supplied by decayed victims) and no circulation. This basin goes completely ignored and unattended for weeks on end yet, many of these clippings have recovered and are doing better in here than in my tank. Look how bright green th P. Stellata sprigs are. There is also no algae. Now, why is this? My conclusion is that the very low light significantly reduces the uptake demand and therefore significantly reduces the stress of high growth demand when in the presence of inadequate CO2 and nutrients.

    Now, I suppose I could test the water for NO3 and PO4 but what would the results tell me? Nothing more that what anyone can see in the photo. That whatever concentration level is in the water is good enough for the level of light and the current environmental conditions in the basin.

    As bizarre and counterintuitive as it may seem, lowering your light may prove the best medicine.

    Cheers,
     

    Attached Files:

  6. Carissa

    Carissa Guru Class Expert

    Joined:
    Jun 8, 2007
    Messages:
    678
    Likes Received:
    0
    I only have 38 watts of light on the 32g tank. The lighting has not changed.

    I'm actually looking into increasing my lighting by overdriving my lights, because the plants that are not directly under the light are somewhat spindly.

    How much is too much, when it comes to nitrates, phosphates, potassium and iron? At what point should I be worried about harming the fish? I don't want to chase test kit measurements around, but it's obvious that there is some kind of deficiency in my tank even when following the standard ei dosing rules. How far can I overdo it before I cause problems?

    Every day I am removing a small net worth of dead leaves now. The problem is not abating although the plants are still growing, slowly. New growth appears good. Perhaps all the leaves that were grown under co2 will die off? The tank is filled with hygro, which is fast growing and likely needs more nutrients than the average plant.
     
  7. VaughnH

    VaughnH Lifetime Charter Member
    Lifetime Member

    Joined:
    Jan 24, 2005
    Messages:
    2,913
    Likes Received:
    44
    38 watts for 32 gallons will necessarily mean very slow plant growth, no matter how much fertilizer and CO2 you add. If you just about double that light you can then use EI fertilizing rates and the CO2 will be necessary. Light determines the growth rate of plants, assuming adequate fertilizing.
     
  8. Carissa

    Carissa Guru Class Expert

    Joined:
    Jun 8, 2007
    Messages:
    678
    Likes Received:
    0
    I don't mind slow growth. I just don't want my leaves to develop holes and die. But when I was doing co2, my hygro grew like crazy. Lighting is not the issue, the plants were doing great under the same lighting for a long time.
     
  9. Carissa

    Carissa Guru Class Expert

    Joined:
    Jun 8, 2007
    Messages:
    678
    Likes Received:
    0
    Well, I decided today that the only way I will find out if it's nutrients or co2 is by trying co2 again. If the plants suddenly stop losing leaves every day, I'll know. I'm at least going to attempt it, whether it will work for me or not is another question. The low ambient temperatures in the room make it tempermental, or at least that is my theory.
     
Loading...

Share This Page