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Why water change day seems to grow aquatic plants better

Discussion in 'CO2 Enrichment' started by Tom Barr, Nov 17, 2012.

  1. Tom Barr

    Tom Barr Founder
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    Basic simple question: why do my plants seem to grow better/best the day of the water change?

    I do a large water change in the morning right after the lights come on, then late in the day, there is mad pearling and obviously better growth than any other day of the week.
    I've measured plant growth to confirm this also. (stem length and biomass).
    I've also done back to back water changes over the entire week, once a day, same time.

    I've suggest a few hypothesis:

    1. CO2 rich tap water. This is supported and suggested in the Optimum Aquarium(1986) from Dupla's Horst and Kipper, often around 20-30ppm ranges.
    One can/could test this by allowing the water to sit for a 1-2 days to degas, then change the water.

    Results, we still see an increase in growth.......but this is inconclusive.
    I agree there is some strong effect here.

    2. Temp differences within a sealed hot water heater and cooler tap water degas once released into the aquarium= cool water holds more gas, O2 and CO2 etc. Same issue as above, plenty of gases available to help growth. Test similar and similar results to above #1 as well.

    3. Exposure to air. Plant aerenchyma (think a sponge in water and squeezed, and then out of water and squeezed) acts like a sponge and takes up lots of gas/air and then uses that while exposured during the water change. Larger water changes seem to produce this effect.
    Test: large water changes by continuous drain and fill methods vs big drain and then refill after exposure. Seems to be plausible. Results suggest the same. You still need to allow and account for the degassing of the tap water also.

    4. Indirect O2 addition= > drives bacterial cycling much faster= . indirect impact on plant growth.

    5. Gas films. This was discussed by Ole in TAG, vol 23, No#1, pgs 32-39
    A physical gill that improves submersed O2/CO2 exchange in some wetland species. If you add enough CO2, then the gas films do not have any difference in growth rates with/without the gas films(see Fig 7). This is similar to exposing the plants to air during the water change.
     
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  2. Matt F.

    Matt F. Lifetime Charter Member
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    I have often wondered why this is, and I have attributed it to co2-rich tap water, which is often times cooler than the tank temp. Be interesting to see if anything can be said conclusively. FWIW, that is what I am doing 2x per week water changes now. Plants just seem happier.
     
  3. Tom Barr

    Tom Barr Founder
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    The conclusive may be elusive.

    But it will give folks some plausible hypothesis
     
  4. krandall

    krandall Prolific Poster

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    Another possibility is that the tap water may contain macronutrients that give the tank a boost. My tap water contains 3ppm phosphate. This can be tough to deal with in a new tank, but when added to an established tank during water changes, it gives the plants a great boost! Because they are galready growing well, they use up all the phosphate made available by the water change by the next day.

    I'm sure this isn't true for every water supply, but it's something to look at. Also, if you live in an agricultural area, there can be nitrate in the tap water.
     
  5. Tom Barr

    Tom Barr Founder
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    Yes, good point.

    The PO4 laden tap water is exactly why we dose PO4 today:) I had no clue till Steve Dixon tested my tap.
    I just knew large water changes made the tank grow better than Steve's, it pissed him off for quite sometime. It's one thing seeing it on line over the web...........but Steve was seeing it in person.

    I think some of the Dutch folks mentioned their Tap, as well as a lot of English and Germans have high NO3 and sometimes PO4.
     
  6. Matt F.

    Matt F. Lifetime Charter Member
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    According to Steve Dixon's analysis of San Francisco water, I doubt the minute level of nutrients in our tap water is the catalyst for the boom in growth we witness, esepcially when a bunch of us utilize the EI as a guide for dosing. I just don't think an extra .05ppm of phosphate or the .25ppm of ammonium will not make a significant difference, but I can't say for sure. The water change/nutrient explaination might explain things for those of us who don't dose anything at all. When it comes down to it, I get a benefit from more frequent water changes with ultra-pure water. Our hypothesis would have to address this disparity. It's going to be hard to test b/c nutrient levels from water sources differ.

    CO2, again, we see a spike, but for those of us who inject CO2, how much difference does this actually make?

    O2 might be our kingpin. The connection between microbial growth and plant health is beyond me, but, imo, a worthwhile avenue. Then again there is less info out there on the direct link (if there is any) between plant health and O2.

    Another thing to think about is the effect of sediment build-up on plant leaves and its effect on photosynthesis. If a plant's leaves are covered by detritus, bacterial slime, or algae is it safe to say that photosynthesis will decrease due to the mechanical interference (blocking the light)? Maybe water changes removefilm, dust, and debris that settles on the bacterial slime that coats the outside of plant leaves. Maybe the plants can utilize more of the light when the leaves have been washed clean by fresh water? This would explain why more frequent water changes increase plant growth--aside from the gas/nutrient explainations.

    More grist for the mill.
     
  7. dutchy

    dutchy Plant Guru Team
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    I have to agree with Matt here. When I change water, I actually reduce the nutrient level. Plants will pearl like crazy afterwards, but isn't this because I just added water that is more O2 saturated? That way we conclude that plant growth is better, but maybe it's just wishful thinking.
     
  8. Marcel G

    Marcel G Banned

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    This reply I found in another thread here on this forum (see http://www.barrreport.com/showthread.php/2316-Plant-bubbles).

    There's also another good thread about the same topic here: http://www.barrreport.com/showthread.php/9895-struggling-to-find-CO2-balance-and-water-change-clues.

    Some useful reading related to "pearling":
    - http://www.barrreport.com/showthread.php/7121-Pearling
    - http://www.barrreport.com/showthread.php/9025-Pearling
    - http://www.barrreport.com/showthread.php/6756-pearling
     
    #8 Marcel G, Nov 20, 2012
    Last edited by a moderator: Nov 20, 2012
  9. Tom Barr

    Tom Barr Founder
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    Well, in some cases, the ferts would, in others not.
    There may be multiple reasons for a positive response due to water changes.

    The observations do not imply there is one sole cause, same for algae issues etc.
     
  10. mi5haha

    mi5haha Prolific Poster

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    Just ignore the bubbles on the tank and plants after the tap water change. If you use a powerful Co2 reactor to inject air (not Co2) into the tank, you can witness bubble all-covered plants and tank in 30 minutes.

    The thing is that It is said (also a known practice) in keeping discus, that frequent water changes (just water, almost everyday) will stimulate the growth of discus. They grow bigger than those in tanks with more food but less water changes.
     
  11. Tom Barr

    Tom Barr Founder
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    Most aquarist have already seen how poorly the plants grow with strong aeration..................
    Versus how well they grow with large frequent water changes.

    The Aeration is highly counterproductive with CO2 enrichment, bubbles alone are not what I'm talking about.
    I'm specifically talking about the plants.

    Do they look and grow better with more frequent water changes?
    If so, why?

    Bubbles on the sides etc, degassing, more gas coming out of solution only takes so long.................so say I do a water change at 9 am, then around 5 pm, I look at my tank and measure the O2.
    Plants are pearling like mad, the bubbles on other things like rock and wood, glass etc...........are long gone
    O2 is about 0.5- 1.0 ppm higher.

    The O2 will degas fairly quickly from the water change with a wet/dry filter and prefilter skimmer............unless plant growth is resupplying the O2.
    O2 makes an excellent metric to measure live plant growth production differences.........in situ.
    I program my Hach O2 to data log and compare the water change day vs the non water change day.

    Spot reading with cheaper O2 meters can be done also. Or colormetric test etc.

    After 8 hours etc, the gas from the water itself will be dissapated, leaving only the effects/influence of vigorous plant growth to pearl and produce more O2. Another thing also occurs when a water changes is done: COD/BOD (chemical or Biological O2 demand) is reduced. Organics are removed (and bacteria that consume and break those organics down- they use O2 to do that).........thus the aquarium has less O2 being consumed, so more is left over.

    With intense pearling, I also think the sticky bubbles also pull off periphyton algae on leaves, and when the rate of growth is rapid, there's less time for the algae to colonize those same leaves.
    Bacterial cycling is increased/enhanced.

    In lower energy tanks, I think these effects are less pronounced..........due to the more efficient cycling rates. Things adapt better and are more stabilized.
     
  12. Matt F.

    Matt F. Lifetime Charter Member
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    I wonder if it's possible for someone to measure co2 and o2 in a tank that gets once a month water changes (low-tech), one that gets weekly water changes, and one that gets frequent water changes (every day). Maybe if we could see some simple line graphs... I know ADA suggests daily water changes sring set-up (2 weeks), because it's said to add vital nutrients and minerals (could be a generic marketing explaination). But ADA even touts that daily water changes increase growth rates. I'd like to see some data, though.

    I think that there is something to the COD/BOD. Even in lower light moss and java fern low-tech tanks, I notice a long term difference when one changes the water more frequently. Healthier plants, less algae, better growth. We have an eclips6 system with sand, java ferns, and moss.
     
  13. Tom Barr

    Tom Barr Founder
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    I agree with ADA on this, I know Amano, well, ADA or someone there at least.........did some O2 test. Amano is very pro Sump/overflow systems for larger tanks.
    If he did a similar test that I did on canister vs wet/dry and managed to reduce/prevent outgassing, then hell hold the same view as I do.

    I also agree if you do daily water changes............you will get more growth, I've ramped up water changes to 3-4x a week and compared them to changes once a month in the past. Hueg difference over time in the growth. Very easy to see.
    If you try and compare only 1 day's worth of growth , it's very hard. But an entire month's, well.....that's very easy.

    Every a week's worth is a huge difference.

    So change the water daily 50% and compare the same tank and CO2 at water change once a week 50%.
    You should see a noted difference.

    This works if the plant biomass is relatively the same for each test run.

    1. So if you trim, then do the Test no#1.
    then observe etc..........

    2. Then you do the same trim, then do test no#2(say daily water changes) then observe......

    3. Repeat this 3-4 times and switch the order............between the treatments, say the daily in test 1#, and then weekly in test 2# etc......you should arrive at a decent answer.

    This requires only 1 tank and is replicated quite well vs trying to have 2 identical 20 Gal test tanks.
    Time blocks are the replicates on the same tank instead of actual replicates on 2 or more 20 Gallon tanks.
    Takes longer, but it a lot more practical for hobbyist wanting to run a test.

    Pruning can get around the differences in biomass.
     
  14. captnphil

    captnphil Junior Poster

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    Sorry if this is dumb but...
    Could it simply be the transparency in the fresh non organic saturated water?
    Or is a simple evolutionary response from the plants to the signs of rain and incoming nutrients...
    Add that to the above factors i barely understand.
     
  15. Gerryd

    Gerryd Plant Guru Team
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    Well as for transparency, my water is slightly cloudy AFTER the water change and is much more clear during the week assuming that c02 is also off. But this is just visual observation in one tank by one person :)

    I like the second thought as there is so much we do not know in these areas...

    We now that plants and animals have environmental triggers during wet and dry seasons for example..

    I will do a simple test and perform a 50% water change DAILY on my 220 for the next 7 days and post pics daily. I will try and get some of the same shots/pov or plant sections to compare. At the least, it should provide a nice boost for my tank even if I cannot capture it digitally...

    All that aside, my experience over many years now is that water changes are beneficial in many ways assuming a proper conditioner is used.
     
  16. Tom Barr

    Tom Barr Founder
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    This would suggest something like tannins etc.......but tannins really do nothing for growth except lower the light a little bit perhaps.
    Testing the organic fraction of growth is EXTREMELY easy for a hobbyists.

    So how does one do it?

    Add some activated carbon and change it every 2-4 weeks.
    It'll remove selectively, large organic fractions.
     
  17. serrano007

    serrano007 Guest

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    hi from spain, i live in madrid nd the water is very soft, Kh 2, GH, 3, NO3: 0, PO4:0, de discus can live in that tap water, jeje.
    I observe the same thing, gorgerous grows of plant the day of water change, nd i ve high levels of CO2 ( 70), with ventury sistem in one of my ehim filters., even in good condition of oxygenation nd CO2 levels, the grow of plants nd bubbles is spectacular with the WC.
    I think is the CO2 nd the level of Oxigenation of the tap water, what do you think tom?
     
  18. Tom Barr

    Tom Barr Founder
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    Well, all dissolved gases, not just CO2, are present in tap water, since it's colder before it comes into our aquariums. It's also is in a sealed chamber: the pipes and plumbing. So what happens when we heat water? the gases are now in excess, whereas as say 10 C they are okay, but now at 27C, they are not and well above 100% ambient conditions.
     
  19. Likuid300

    Likuid300 Junior Poster

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    Maybe much like free radicals in our bodies, there's some single oxides hanging around in the tank which impeed co2/nutrient/light uptake some how? Would be less likely to happen without added ferts, eg. less random pairing/cleaving of electrons and more like nature and balanced. But when you do these large WCs, balance becomes restored and plants, much like humans, start running at optimum levels again.
     
  20. Matt F.

    Matt F. Lifetime Charter Member
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    I can't help but think it has something to do with the flow of new water in our systems. In lakes and streams, there is a constant flow of fresh/new water at any given time. The more we can replicate this in our aquariums, the better (be that a wet/dry or more frequent water changes). I think amano has fresh filtered water introduced in his home tank constantly. Of course the common aquarist can't afford to have a system like that, but there seems to be a strong correlation between the supply of fresh water and plant growth (along comes with this a reduction of overall algae).
     
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