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How much surface ripple

Discussion in 'General Plant Topics' started by VaughnH, Dec 21, 2008.

  1. VaughnH

    VaughnH Lifetime Charter Member
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    I know it is important to keep the water surface rippled to increase O2 absorption by the water, to keep surface films away, and to help drop the CO2 concentration at night. I have my Koralia powerhead pointed upwards a bit to get that ripple. Does the amount shown here look adequate, too little, or too much?
    [​IMG]

    [​IMG]
     
  2. SuperColey1

    SuperColey1 Guru Class Expert

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    Looks OK to me. I have it like that 24/7 by having my Lily pipe partially above the surface (Maybe a quarter or a third above), then a Koralia further down deals with the circulation.

    I do of course have to use 3bps instead of 2 to compensate for a little loss.

    AC
     
  3. Mooner

    Mooner Lifetime Charter Member
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    Hi Vaughn,

    For comparison here are two tanks. First pic is a canister filtered tank and the second is an overflow tank.

    [​IMG]

    [​IMG]

    More surface agitation on the canister tank due to the overflow having normal degassing. Each tank is different as you know and there is a trade off to more agitation = more CO2 loss.

    Another aspect is the changing water level of the canister tank when using a fixed method of surface agitation. Evaporation causing more agitation therefore more degassing of CO2 and increase of O2. I suppose the ideal would be a top off system, but right now it's me every day.
     
  4. VaughnH

    VaughnH Lifetime Charter Member
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    Thanks for the pictures. Your ripple looks about like mine, perhaps a bit more. I don't mind the need for extra CO2 due to the ripple. In fact that is an advantage, because it means the CO2 level drops more quickly with the CO2 off at night.

    I think I will go raise my Koralia a half inch or so to get a bit more ripple. And, increase the bubble rate a bit to compensate.
     
  5. ntino

    ntino Guru Class Expert

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    Why not just inject water with air? it makes alot more sense than chasing after ripples. also, as tiny bubbles rise, they promote CO2 offgassing if you think its a big deal, although I have personally never seen a difference between a tank that offgasses at night and one that doesnt.
     
  6. VaughnH

    VaughnH Lifetime Charter Member
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    The primary purpose of having a rippled surface is to get more O2 into the water. Air bubbles rising through the water don't put much O2 in the water, since their surface area is so small. The primary effect they have is to ripple the water surface, so it makes more sense to obtain that ripple with the powerhead which is already there to get water circulation.
     
  7. Naja002

    Naja002 Prolific Poster

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    Just wanted to added some input here. These are vidoes of my 55g setup:

    55g
    Catalina 4 x 54w T5HO
    Pressurized--dual outlet: Magnum 350 reactor and powerhead mist.
    Photoperiod: 9 hrs total = 1hr@108w + 7.5hrs@216w + 0.5hr@108w
    C02 comes on 2hrs before lights and goes off 30mins before lights
    Immediate 10% daily WC at the end of the photoperiod
    Dropchecker
    pH controller


    Video 1--shows right side surface turbulation
    followed by the xP source followed by the left
    side surface turbulation followed by the magnun
    350 source head on:

    [​IMG]





    Video 2--shows pH just prior to WC followed by the gas buildup in the magnum 350 C02 reactor followed by the
    end of the drain cycle followed by the end WC pH and gas build up:

    [​IMG]


    The WC takes about 2 mins to drain and about 30 mins to fill--the xP out out it exposed for about 1/2 of that time. pH actually shuts off at 6.1 (probably 6.19, 6.18) and comes back on 0.2 higher (6.3). The rise (degassing) shown in
    the video varies from ~0.1-0.15....it's not actually 2 full points.....depends upon where the start/stop 6.1? is.....:rolleyes:
     
  8. Henry Hatch

    Henry Hatch Guru Class Expert

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    Vaughn,

    I have less surface rippling than the tanks I've seen here. I look to have movement without actually breading the surface. I drop a flake of food in the tank to see how it moves. At the moment I have just one co2 tank which is diy. I am concerned about outgassing using diy since ican't crank up the bubble rate. Based on my drop checker I have been able to maintain 30+ ppm.
     
  9. SuperColey1

    SuperColey1 Guru Class Expert

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    Thats the 'trade off' with DIY though. The money saving means less options to increase / decrease injection plus you can't turn it off at night or you lose the pressure and the mix also suffers.

    I ripple my surface because I am heavily planted, heavily stocked and therefore I tend to get a bit of film/scum on the top. With a ripple this doesn't form and I just up the injection a little to compensate.

    This also means degassing quicker therefore as long as it isn't too quick the fish get the benefit of much less CO2 a lot quicker.

    AC
     
  10. VaughnH

    VaughnH Lifetime Charter Member
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    I don't think a surface ripple like shown in the photos will work well with DIY CO2, because of the loss of too much of the limited supply of CO2. But, no one using a high light intensity on a tank bigger than 20 gallons or so is likely to have continued success using DIY CO2 anyway, so this is really for pressurized systems. And, the goal here is to quantify what is good surface rippling and what is too much or too little.
     
  11. ntino

    ntino Guru Class Expert

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    I dont really think you are right about this - you inject CO2 into the water, why not air? I'm not talking about an airpump, rather a venturi or a wheel mesh/needle wheel. Air is 20% O2 and O2 is more soluble in water than CO2. To me it would seem that its tons more efficient than splashing water around :)
    I have tried doing this and my O2 is around 17ppm in the morning, thats a while after shutting the air injection off, but then again, my bubbles dont rise through the water, they are so small that they just hover around.
     
  12. VaughnH

    VaughnH Lifetime Charter Member
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    CO2 is at least 100 times more soluble in water than O2. It is easy to dissolve CO2 in water, but not easy to dissolve O2.
     
  13. ntino

    ntino Guru Class Expert

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    errr, you are right, I am wrong. Its however its only about 23 times more soluble - I assumed otherwise becaues of lower molecular weight for O2 still dont know why...Diffusion rate is greater for O2 which makes sense to me.

    Does anybody know why Co2 desolves better? I tried looking online and couldnt find it.

    However I do still have around(upper limit of test kit) 17ppm compared to 8 to 5 that most people would have.
     
  14. VaughnH

    VaughnH Lifetime Charter Member
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    Solubility of Gases in Water
    CO2 is 90 times as soluble at 20 degrees C as O2 is. I was off a bit with my estimate. (Just nit picking here:eek: )

    I believe the reason for the higher solubility is that gases which chemically combine with water have higher solubilities. Check the solubility for NH3, for example.
     
  15. ntino

    ntino Guru Class Expert

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    According to that its only 50 times, but if you google it, there are a couple of medical papers saying 23 times... I dunno, but either way, try injecting air via mazzei and see what it does to O2 content - it works for me, and all you need is another solenoid on a timer.
    Btw, i dont think CO2 can combine with water any more than 02 can.
     
  16. kid creole

    kid creole Prolific Poster

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    If CO2 is so soluble, could you put air through a reactor and up your CO2 levels?
     
  17. ntino

    ntino Guru Class Expert

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    Co2 levels in atmosphere are very low i think like 0.03 percent. compared to O2 which is 20%
     
  18. Tom Barr

    Tom Barr Founder
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    Yes, you could do that, if..............we burn every available fossil fuel, and wait about 1000-8000 years.

    Then bubbling the CO2 enriched air would give you about 25ppm.
    The issue is the rate of diffusion is so slow in water and boundary layer formation.
    10,000 slower and 10,000 more energy required to overcome that.

    We can dramatically help that by increasing flows and concentration.
    That's why we get 1000%-2500% faster rates of growth.

    Nutrients ike N and P are small potatos.

    Also, a word of warning, just because it's on the web does not mean it's correct.
    Never stake your life etc on it;)

    Oxygen Solubility in Fresh and Sea Water

    This is a good graph of O2 and air in both FW and Marine.
    Here's a calculator:

    Oxygen Solubility

    Knock yer selves out.

    CO2, let's consider CO2 and O2 for fish and plant CO2 uptake across a membrane within a discussion:

    Carbon dioxide Solubility in Lungs

    Ah.........it may be very different once we add a lipid membrane in the way huh?
    A polar solvent and non polar gases (Think oil and water), but CO2 ionizes from CO2 to form polar HCO3 etc, O2 does not. So you end up with a lot more CO2 being able to dissolve than you might predict just looking at the non polar gases.
    O2? Not much. Same for N2 gas.

    This is a fun question and stumps many.
    The above gives a reasonable quick guide about why.

    Here's another good discussion about CO2, O2 and also N2 as a non polar gas as well(not bad to look at other like situations)
    :
    Applied Aquatic Ecosystem Concepts - Google Book Search

    This gives yet another ratio between O2 and CO2. Since we deal with biological systems(plants, bacteria, fish, inverts etc) and things having to go across membranes, I'm more inclined to go with the 20:1 ratio.
    Note, for us and for fish and plants etc..........all gas exhgcnage goes into "water solutions", not as a "gas". Your lungs dissolve O2 and CO2 release etc from liquid solutions(blood).

    If you look at pH's effect on CO2 solubility, as many new hobbyist do, you might think that simply lowering pH will give you more CO2.

    No..........it does not! Adding salts or pH lowering chemicals that are not carbonates etc, will not does this with CO2.

    If you want more CO2, add more CO2 gas. This is rather self evident, but folks confuse themselves and others confuse them even further by not understanding it either. The pH is determined by how much KH is there, not pH in and of itself directly. Yes, you can dissolve CO2 more easily(more will be in the form of CO2[aq]), but this really does not matter much since we add gobs of CO2 gas anyway. That's the part that counts for us.

    KH/pH will vary at equilibrium from many folk's differing tap waters. So do not concern yourself too much with that, stick with KH and CO2.
    Focus there.

    But do not try and save all the CO2 etc you can either while ignoring O2.
    Make sure to have a good amount of O2 for the rapid biological cycling of waste and for fish health and vigor.

    CO2 dissolving efficacy is mildly important, we can always turn the valve a little bit more one way to adjust the CO2. O2 needs more exchange with the air most of the time and the little CO2 loss is easily made up for. During the day/light cycle, O2 is high from plants/algae etc.

    So it's less important to crank the surface movement.
    So night time aeration while not needed typically, can be done also.

    I prefer good current all the time so that makes up for the aeration and I just add a bit more CO2 for the 8-10 hours of light I use.

    But...............you can do that+aeration at night also.
    This is a redundant 2nd back up, and also provides even more room for error with CO2 in case you added a bit too much for the fish during the day, it's quickly blown off at night. The higher current keeps the surface scum at bay, adds O2, and mixes the CO2/nutrients very well, so that's a good thing whether you use aeration or not.

    They complement eachother redundantly.

    Now...........all this is far more complex than many hacks on the web will suggest, they gloss over CO2, barely mention O2.......and then blame nutients for every woe they have and how their own unique method will cure all that ails ye. I make no such claim, I've long said CO2 is the root of 95% of folk's issues. I might consider 80% and then 15% O2. 5% the rest. If you look at light and do not simply assume whatever light they have and adjust CO2 from there, then light is about 40%, CO2 about 40% and O2 about 15% and nutrients about 5%(and the easiest to manage/test with confidence).

    If all you have is 1/3 of what plants use to grow to base your ideas on and are able to test, then it's no wonder there's too much focus on nutrients by hobbyists.

    So they are hardly to blame.

    Regards,
    Tom Barr
     
  19. The Rockster

    The Rockster Guru Class Expert

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    Hi, Would it be a good idea, for me to turn my airstone on, after the lights and auto CO2 system turn off. I have some surface scum, that I have been living with, although its not real bad, and disappears after the weekly W/C. The scum is probably due in part to the feeding of live California Blood Worms, and the heavy Discus bio load.
    After reading this thread, I am contemplating the above course of action hoping it would benefit the fish and plants.
    I have an airstone wand along the bottom of the back wall. Only used it when I had a nitrate problem after rescaping the tank.( I know that most would not use airstones in a plantedtank.)
    I have ecological issues with waisting CO2, so rippling the water, to me is not an option, nor is purchasing powerheads or other components. Although I do have flow around a lot of my tank, controlled by my Eheim cannisters, and their spray bars.
    The reason I post this question is that I am not experienced enough to realize the negatives verus the benrfits of adding O2 to a plantedtank at night, and if its even worth it.

    Happy New Years!!
     
  20. VaughnH

    VaughnH Lifetime Charter Member
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    It would be a good idea to run the airstone at night. In fact, one of Tom's susggestions several weeks ago, was to hook up the CO2 system so it puts air into the tank when the CO2 is off, like with an air pump that is shut off during the day and is on at night. Air bubbles also provide surface rippling, and I think that is their primary benefit.
     
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