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How come plants grow so fast after water changes?

Discussion in 'Advanced Strategies and Fertilization' started by freemann, Feb 22, 2006.

  1. freemann

    freemann Junior Poster

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    Hi all
    I am really wondering on this one.
    Ok we talk of high light, high CO2, all ferts EI wise aquarium.
    I have observed it repeatedly, when I do wc changes and I do 2 of them (50% each) every week, in the first 24 hours even if I do not dose ferts over this period, plants pearl like crazy and grow incredibly faster even 3-5 cm every day. Also I have observed that the tank kind of "deteriorates" until the next wc. It is one of the things I have not found a credible explanation for in all the reading I have done. Has anyone else observed this? And how do you explain it?
    :)
     
  2. Spar

    Spar Guru Class Expert

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    Re: How come plants grow so fast after water changes?

    My guess is that it is the gases from the water (assuming here that you use tap water) concentrating around the leaves. My tank looks like a massive pearl the same day as water changes as well, but is due to these gases, not actual pearling.

    Not real sure though why the plants grow faster at this time... maybe certain nutrients in your water supply that csm+b / flourish / etc doesn't have? a guess anyway.
     
  3. Tom Barr

    Tom Barr Founder
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    Re: How come plants grow so fast after water changes?

    It's an opportunity. You know the difference between growth and excess gases hanging around? You can tell when a plant is really growing well, vs just having some gas attached to it.

    You are not going to like this nor believe me, but it's CO2.
    If the nutrients are the same, what else is missing that the water change will add?

    Typically good CO2.
    In my tap, I had high PO4, that and the CO2 really drove my plants nuts.

    If you do large water changes, you also expose the plant leaves to the air, where they can take in large amounts of CO2.
    Also, bacteria also get a shot of O2 generally in excess also.
    That and the plants O2 release can drive the system hard for a full or two, then buy the 2-3 day it slows down, and by the week's end, things are much slower.

    If you do 2x a week 50-60% water changes, you'll see mostly excellent growth.

    Means you could stand to add more CO2 if...............and only if you like what you see(all that growth and pearling).

    I mean more pearling than an ADA tank.........

    That water change allows you to see what the potential max growth is when you have non limiting nutients and CO2.

    So that is a very useful and wise thing to observe and use to your advantage when applying steps to improve your aquatic horticulture.

    That is an opportunity to achieve that for 7 days a week.
    CO2 mist can help.

    Think about it and think about the gas exposure to the leaves during a water change.

    Regards,
    Tom Barr
     
  4. freemann

    freemann Junior Poster

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    Re: How come plants grow so fast after water changes?

    Of course I know because the bubbling is expressed in excess growth at the same time so it is expiration. I have even seen it in the past with WC with RO water that was stagnant in a barrel for a week out in the sun.
    As I said there is tons of CO2 all the time in the tank and that would imply lots of O2 as well if plants are using it.
    Tom since last time we talked I have pushed the CO2 even more now it is 6.55 at the point the ph controller switches off and 6.60 when it switches on. I am 100% sure I have tons of CO2 fish are "gasping" all the time (they do not come to water surface but are still gasping) I can see that. So if your theory stands could it be the form of CO2 (bubbles versus diffused) that makes the difference?
    Another possibility and consider this, it maybe a crazy idea, but maybe it is not what water adds but what it dilutes. Or maybe some additional gas that is missing the rest of the time.
    Well that maybe true, more plant mass do come in contact with air through the leaves that float on the surface when the water is lowered.
    So this brings up a question that is moving around my head. Could it be a good idea to switch CO2 off for lets say 5 hours at night and drive an airstone hard in the tank to give plants and bacteria the O2 they need at that time (Would the big ph swing create problem for the fish?)?
    I reckon that meaning CO2 bubbles (and what of the stagnant RO water in that case? (that surely does not have the excess gases.) not simply CO2 because that positively is already there.
    I have excellent growth in most plants yes all the time but some still are not growing that well, furcata, Dwarf lobelia, long leaf Stellata. And the leaf yellowing always lurks around.
    Positively more, boiling.
    You are constantly tempting me on this one; I have a very efficient CO2 through a diffusion distribution system, could replacing it with a bubbling system be as efficient? I mean on achieving this low ph value I get now (or it won't be needed anymore?)? Would a combination of diffusion plus bubble distribution of CO2 be a good alternative? (I could have a wooden stone or 2 before the CO2 switch valve that would run all the time.)

    Regards
    Freemann ;)
     
  5. wapfish

    wapfish Prolific Poster

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    Re: How come plants grow so fast after water changes?

    OK, here's what to do. Take the water from your tank after the next WC and save it for a week or more letting the gases equilibrate with the atmosphere. It should probably be kept in the dark during this time to prevent any algae growth or whatever. Then, compare the REUSE of this water with the use of FRESH unused water that has similarly been left out for the same length of time. If there is something inhibitory in the used tank water, it should not promote growth as well as the fresh water.
     
  6. pigwiggle

    pigwiggle Junior Poster

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    Re: How come plants grow so fast after water changes?

    I’m skeptical of the CO2 explanation also. Before a water change I let the replacement water sit in a bucket for a day or two; I warm it and let the chlorine outgas. I have to assume that after a couple of days any excess CO2 would have outgased as well. Yet, when I replace my CO2 enriched aquarium water with the “stale” replacement water I also see active pearling. I assumed it was some trace or other I was missing.
     
  7. Tom Barr

    Tom Barr Founder
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    Re: How come plants grow so fast after water changes?

    Well, all you have to do is change the additions to higher dosings, EI is useful, you can even bump things up higher than that if you wish.

    The amount of accumulation of organic fractions is not a huge effect, not to the extent you see the increased pearling and the dramatic increases in growth...........

    So while you might skeptical of the CO2 explaination, it holds more credence than the other possibilities..................

    I've also seen and maintained that same growth and pearling etc you see all week and for several weeks without water changes..............

    Co2 was the main key.

    And given it's role in aquatic plant growth, it makes the most since in terms of increased plant growth, homrones, allelopathy, DOC etc..........none of that fits well.........nor do they produce dramatic impacts on growth, nor are they removed that much by 50% water changes, so there is some there all the time.

    Adding inorganic forms of nutrients can help, but if you dose 3x a week, then that is non limiting also.

    You really have only a few choices if you think this through.
    Try the CO2 mist and then see.

    I'll respond more a little while later.

    Regards,
    Tom Barr
     
  8. freemann

    freemann Junior Poster

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    Re: How come plants grow so fast after water changes?

    Well if I do that I will get bits of algae, light is too much.

    Maybe it is something else that accumulates some retarding agent. Maybe the ferts themselves.

    It is a fact that plants get full of bubbles initially after the gases are released from the fresh water, I reckon most of this gases must be air.
    Why would the well water be saturated with CO2?
    I can't disagree on the CO2 assumption but only because I don't know. As you said yourself holds more credence it is not a certainty.

    I can't see me going any lower here without stressing the fish to much.

    Well maybe there is something we miss.

    I dose and test alright :)

    Let me change the lights first and we will see.

    I wish more people experimented and checked things instead of doing landscapes. Well that is me.

    :)
     
  9. Tom Barr

    Tom Barr Founder
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    Re: How come plants grow so fast after water changes?

    Well, the ferts don't do this with my plants, nor ever have, even at very high levels. So that's doubtful.
    Tap would not help growth only to a few days later reduce growth.
    So no retarding agents, if you want to provide a control for reatrding agents: add some activated carbon, it'll remove any of that.

    Did you say well water?
    Hahha, there you go, well water is loaded with CO2!!!!!!!!!!!

    Well water comes from rain, then goes through trh ground, as it does so, it picks up CO2 from bacteria in the soil, often the ground water is extremely high, you also live where there is significant limestone karst.
    Adding CO2 rich water to limestone produces caves by dissolving the CaCO3, as the CO2 degases, it can form stalagmites etc.

    The hunch I had was correct it seems.......
    Your tap is loaded with CO2.

    I can't disagree on the CO2 assumption but only because I don't know. As you said yourself holds more credence it is not a certainty.
    I can't see me going any lower here without stressing the fish to much.
    I wish more people experimented and checked things instead of doing landscapes. Well that is me.

    :)[/QUOTE]

    Well, I do but I also do landscaping.
    The key is some balance.

    I think you can add more CO2, increase your surface movement(this will prevent fish from getting gassed) and consider the mist method.

    I bet you will see what you seek if you do this path.
    Do this path first though, then if you give this a real try, I think it'll solve most if not all the issues.

    While testing is nice, CO2 is one funny thing when it comes to deciding on how much you have.

    Alkalinity has more than bicarb sources and most test methods measure total, not bicarbonate alklinity. Hydroxide ans borate alkalinity can play large roles.

    The temp differences also play a role when you pull the well water up from depth and pressure.

    More gas is held in solution at higher pressure/depth/colder temps, releasing that into a tank, the levels will go up even if they are not enriched by ground water percolating through soil.

    Regards,.
    Tom Barr
     
  10. freemann

    freemann Junior Poster

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    Re: How come plants grow so fast after water changes?

    Still after a WC ph always goes up almost 1 degree and takes long time to go down again through CO2. Isn't that an indication that it is not CO2 but something else?
     
  11. pigwiggle

    pigwiggle Junior Poster

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    Re: How come plants grow so fast after water changes?

    Now that you mention it, I’m using well water also. It’s rock hard. So, can plants strip carbon dioxide from calcium carbonate? They would need to provide some extra protons and somehow keep the carbonic acid around long enough for it to decompose. Anyway, the well water business makes sense. Good call.
     
  12. Tom Barr

    Tom Barr Founder
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    Re: How come plants grow so fast after water changes?

    It's not so much that the well water is rock hard, it's that it's loaded with CO2 and dissolved Ca++.

    When you see dramatic improvements in growth with water changes, it's generally only a few things: CO2 is too low daily, PO4 is rather low at the end of the week, mid week etc.

    Very few things cause such pearling and plant growth, bubbles alone is something different, most folks know when their plants are producing bubbles and growing well, air bubbles dissolve fairly quick also, O2 from the plants keeps on coming.

    Regards,
    Tom Barr
     
  13. Tom Barr

    Tom Barr Founder
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    Re: How come plants grow so fast after water changes?

    The mist method is nice since it's easy to get a huge amount of CO2 to the plants without worrying about dissolved CO2 so much.

    I use to use multiple water changes to rev my tanks up, but I found bumping the CO2 up had the extact same effect.

    Regards,
    Tom Barr
     
  14. geministudios54

    geministudios54 Junior Poster

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    Re: How come plants grow so fast after water changes?

    Hi Tom...Could you describe to me exactly what the 'mist method' is?...What do I need to purchase to achieve this??
    Your suggestions would be appreciated...thanx...Jeff...
     
  15. Tom Barr

    Tom Barr Founder
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    Re: How come plants grow so fast after water changes?

    It's nothing complex other than why it works, a thing of rather hot debate.
    The fact that it does work, it rather simple to see.

    The mist method is simply a concept of delivery of CO2 to the plant.
    It gets away from dissolving CO2 into the water as the primary means of delivering Carbon to the plants.

    We add gas and then blast these CO2 bubbles directly into the plant beds in our tanks, not waiting for the gas to fully dissolve. Some gas does dissolve though along the way.

    The idea is that gas is much faster at transfer across a distance(say the outside of the leaf to the inside) than a liquid. Try breathing liquid sometime.

    The flux, the rate of transfer is dependent on this distance, and the medium it's transfering through as well as concentration.

    This is the basic Fick's 1st Law of diffusion.

    Well, on every single part of Fick's 1st law, the gas wins.

    1. Concentration is defintiely higher than 30-100ppm, the gas in pure form is 1,000,000ppm!
    Even if it's only 1000ppm, it's still huge.

    2. Distance, the gas hits the plant directly and bubbles rise up under the plant where most have their stomata that take in CO2.

    3. Coefficent of diffusion, gas has 10000X higher rates than liquids.

    So you can do the math easily here.

    The method itself is easy and dirt cheap, perhaps the cheapest next to feeding the gas into a filter(Free),.

    You simply use a fine limewood or diffuser stone that produces a fine mist.
    Place this stone under the outflow of the filter so that the mist gets blasted all over the tank well.

    The better the mist travels around the tank, the better.
    I use a solenoid and check valve to turn the CO2 off at night.

    Limewood stones run about 2$.

    You can use a lead plant weight to keep it down or a rock, wedge into the wood etc and use rigid airline tubing also.

    If you target 30-35ppm CO2 and have some extra gas hitting the plants, you get much better results, higher O2 levels than you could before and less impact on fish. You should see pearling after 1-2 hours after the lights are on. With high light, maybe even less time.

    Anyway, you should certainly see a much higher pearlign rate than with any other method.

    You can also see that the closwer you get to the outflows of CO2 reactors of mist type diffusers, the plants grow much better and pearl more.

    All you need to do is mix the mist well and blast it into the plant beds now.
    30ppm of CO2 does not mean the entire tank is equally rich in CO2. The outflow of a CO2 mister is obviously going to have far more CO2 than on the opposite side of the tank and you can see the difference in virtually any tank.

    Mixing and distribution plays a large role.

    Simply adding CO2 mist/bubbles right under a plant can show you the differences vs the ppm in the water also.

    Regards,
    Tom Barr
     
  16. darren_in_the_marsh

    darren_in_the_marsh Junior Poster

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    Re: How come plants grow so fast after water changes?

    gotta reply to this one!

    i was out of town for the last 4 months, and during that time, i did not add one spec of nuts, no water changes, and instructed my wife only to feed the 3 SAE a few flakes ever other night and add water if the level dropped too low. My pressurized co2 was running the whole time, on at night only.

    some quick stats:
    29g
    2x55w pc
    kh 4-5 (baking soda to raise it)
    pH 6.7 (pH probe) diffuse bubbles into an aquaclear, but misting to be installed soon
    gh - super soft

    the result was super poor plant growth and green water like i had never seen it before! I attribute the green water to zero nitrates, seen this before a few times.

    during the last three weeks, i put in my uv ster. to rid the green algae, and have added a few tsp of mgso4, a few drops of cacl, no CSM, no nitrates, but mostly super heavy water changes (>50%) everty 4-5 days, and the plant rebound has been quite steady.

    i have been struggling with my plants for sometime, and nut dosing (super pains to get the 'right' concentrations) has not helped that much, but water changes seem to be the only saving grace.


    the theme on this thread seems plant tanks need near lethal levels of co2, even to point where people are suggesting to agitate the surface water to make sure o2 gets in! i was under the impression co2 diffuses easily out of water, and to make strides to keep co2 saturated!


    i am going to test the co2/water change theory and use fish food and fish waste as my only nut source, cram co2 into the water, and do a lot of water changes. my plants do show signs of being nitrate and iron limited though, the anubias are striped (but growing like crazy) and my sword plant is actually brittle, and veiny, so this experiment may not last too long! the ludwigia is growing really well, though, this seems to be a very hardy plant. also, i have not one inch of substrate left. every cubic centimeter is crammed full of roots, so maybe a little house cleaning is in order.

    cheers, darren
     
  17. Tom Barr

    Tom Barr Founder
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    Re: How come plants grow so fast after water changes?

    Please be very careful about adding lots of CO2.
    Do this incrementally and slowly, watch the fish and plants careful.

    Do not be in hurry here or sloppy.
    :gw :gw
    regards,
    Tom Barr
     
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