Aeration myth?
Tylernt
I posted a few days back about my air-driven RUGF in r.a.freshwater.misc.
Since then I have read numerous archived posts on D*ja that an airstone
bubbling air through the water does not aerate the water; rather, the
movement it creates at the surface (breaking the surface tension) does the
oxygenation thing.
One of the things that attracted me to the RUGF was killing three birds with
one stone: filtration, aeration, and keeping the gravel clean in my FO
freshwater tank. But now it would seem that my fish aren't going to get any
oxygen from my air-driven RUGF, because it doesn't disturb the surface of
the water. The air just bubbles up and out through the vertical updraft
tube. (http://www.thekrib.com/Filters/rugf-dixon.html)
THEN I'm reading about saltwater tanks with a calcium reactor and planted
freshwater tanks, both of which use CO2 injection. The CO2 just bubbles up
through the water. Wait a minute, I thought that gas <-> liquid didn't
happen in the bubbles!
So, what's the story? Has anyone done any tests? Is it really true that
bubbles don't exchange gasses (O2, CO2), with water cuz if so, a lotta
people are wasting a lotta money on CO2 injection that never makes it into
the water.
Furthermore, many powerheads have a venturi that lets you add bubbles to the
output. What's the point, if bubbles don't provide aeration? Isn't the
surface motion provided by the powerhead all that's needed to provide
aeration?
Given the fact that my 4 Zebra Danios have been chasing each other happily
around and have not been gasping at the surface for the last three days in
my fully hooded tank, I think the "aeration doesn't happen in the bubbles"
is a myth.
So... prove me wrong! :)
Thomas Coon
extremes. Yes the bubbles do provide *some* air exchange. Does this
appreciatively increase the available O2 in a system? Not really, compared
to the increased air exchange by breaking the surface tension of the water.
Circulating the water at the top to improve O2 saturation is doing far more
than the bubbles could.
Venturis on power heads baffle me. I think a lot of this is for the gee
whiz effect in a FW tank. I wish they would stop putting them on P heads.
Sure many people use them (venturis) for applications that they weren't
designed for but the only reason I can figure for them is to verify flow in
a PH configuration.
4 Zebra Danios isn't nearly enough IMO to tax the O2 exchange in even
the smallest of tanks. (10 gal)
Just my opinion. Some of the more scientific minded may correct me on
some details but the over-all idea is sound
--
Tom
http://home.twcny.rr.com/trmrcoon
"Tylernt" <tyl...@NOSPAM.bigfoot.com> wrote in message
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The Stare
"Tylernt" <tyl...@NOSPAM.bigfoot.com> wrote in message
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Here is a post i saved from an discussion on the subject :-)
(scroll down)
--
Bill T
I think I need a new sig line.
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From: Dave <da...@spamcop.net>
Newsgroups: rec.aquaria.freshwater.misc
Subject: Re: Aeration myth?
Date: Thu, 05 Jul 2001 11:34:06 -0400
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Stephen Hinchey wrote:
> I'm a bit confused here. I've been hearing from people that the only
> means by which an air pump aerates the water is by the bubbles hitting
> the surface and thereby agitating it. What about the bubbles themselves?
> How DON'T they aerate the water? As they rise won't the gases dissolve in
> the water? And wouldn't that be the idea behind an air stone-- create
> finer bubbles so that there is more surface area and therefore more air
> will dissolve in the water?
>
> * Steve
Enjoy :-) --->
From: Andrew S Dalton (ASDALTON@[remove.this]prodigy.net)
Subject: Re: Why wouldnt't bubbles oxygenate?
Newsgroups: rec.aquaria.freshwater.misc
Date: 1999/01/25
Jeff Cochran wrote in message
[snip]
>
>In theory, it sounds fine, in practice it doesn't actually work.
>Bubbles do provide an air/water surface for gaseous exchange, but the
>problem is that surface area isn't in contact with air for any
>significant amount of time.
Since my background is chemical engineering, I'll inject some real mass
transfer theory into this discussion.
Time of contact isn't an issue in this situation. While each individual
bubble is in contact with the water for only a short time, new bubbles are
constantly being generated, and the overall effect is that a certain number
of bubbles are always dispersed throughout the water.
The rate of transfer of mass (r) is directly proportional to the surface
area (A). It is also proportional to the driving force, which is the
difference between the saturation (equilibrium) concentration of oxygen
(C*), and the actual concentration (C). But there's still something
missing, because we know that an agitated tank tends to be better oxygenated
than a stagnant one when everything else is equal.
That missing parameter is the mass transfer coefficient (k). This
coefficent is strongly dependent on the amount of turbulence at the
air/water interface, which explains why agitation in an aquarium is
desirable.
The overall equation is this: r = kA(C* - C). In an aquarium, A is close to
constant, even if you inject bubbles. C* is always 7 ppm, and we try to get
C as close to C* as possible. So the only thing that's left to change is k,
and we do that by agitating the water with an airstone or pump.
>
>The second theory posted in this thread of airstones and the bubble
>stream agitating the surface also doesn't hold water (bad pun,
>sorry...). Again, agitation of the surface doesn't cause any exchange
>to occur faster.
Yes, it does. Mass, momentum, and heat (think of the wind chill factor) are
all transfered faster when there is turbulence at the interface.
>
>Water in contact with air will exchange gasses until an equilibrium is
>reached. Depending on the salinity, alkalinty, temperature and
>original gas content of the water, the exchange that oxygenates the
>water may take place at different rates, but it's not a supremely fast
>process. Still water will eventually reach equilibrium just fine.
Not if your fish are consuming oxygen. What the water will reach is steady
state, isn't the same thing as equilibrium. As I said earlier, the
equilibrium concentration of oxygen in water is 7 ppm. However, the steady
state concentration in a poorly oxygenated tank can be considerably less.
If the mass transfer coefficient is high, the steady state concentration
will be only a little less than the equilibrium concentration.
>
>So what actually does the airstone help with, if it's not bubbles and
>it's not surface agitation? It's water movement. Each small bit of
>water needs to touch an air surface to exchange gas
Surface agitation facilitates microscale water movement by carrying
well-oxygenated water at the surface into the less oxygenated bulk fluid,
and by carrying oxygen-depleted water from the bulk fluid to the surface.
If two aquariums have equal water movement (in terms of large-scale water
flow), the one with the greater surface agitation will have a higher rate of
oxygen transfer.
----------------------------------------------------------------------------
Andrew Dalton
To reply, remove [remove.this] from my address.
Macbrush
1. Bubbles are a lot finer with a CO2 reactor compare to ralatively cheap
airstone.
2. CO2 bubbles are near 100% CO2 vs air bubbles areapprox 21% oxygen.
Add two factors together, the O2 dissolve rate via air bubbles in water can
easily be hundreds of times less than pure CO2 bubbles (speed of gas
exchange "drops exponentially" as its gets closer to equalibrium).
Hope this helps
Kenneth
"The Stare" <wa...@not.likely.frontiernet.net> wrote in message
news:9khgv8$3rdg$1...@node21.cwnet.roc.gblx.net...
Empty
<ozXa7.187648$EF2.25...@typhoon.nyroc.rr.com>:
> Venturis on power heads baffle me. I think a lot of this is for the
> gee
>whiz effect in a FW tank. I wish they would stop putting them on P
>heads. Sure many people use them (venturis) for applications that they
>weren't designed for but the only reason I can figure for them is to
>verify flow in a PH configuration.
I use the venturi on my powerhead as the CO2 input on my tank. The venturi
does an admirable job of dispersing the CO2 bubbles and ensuring that the
high-CO2 water makes the rounds correctly.
CO2, by the way, dissolves into (and out of!) water MUCH easier than O2.
~Empty
--
"...felt like I'd been hit by a sex truck"
-Nyx
http://www.emptiedout.com/
Chuck Gadd
<tyl...@NOSPAM.bigfoot.com> wrote:
>I posted a few days back about my air-driven RUGF in r.a.freshwater.misc.
>Since then I have read numerous archived posts on D*ja that an airstone
>bubbling air through the water does not aerate the water; rather, the
>movement it creates at the surface (breaking the surface tension) does the
>oxygenation thing.
Yes, the water movement at the surface is the main method Oxygen gets
dissolved into the water.
>oxygen from my air-driven RUGF, because it doesn't disturb the surface of
>the water. The air just bubbles up and out through the vertical updraft
>tube. (http://www.thekrib.com/Filters/rugf-dixon.html)
Any water movement on the surface will improve O2 exchange. An
airstone creates water currents, which pull water from the lower part
of the tank up to the surface, and water containing O2 flows down.
Since the water now reaching the surface will have slightly less O2,
O2 will diffuse in from the air.
>THEN I'm reading about saltwater tanks with a calcium reactor and planted
>freshwater tanks, both of which use CO2 injection. The CO2 just bubbles up
>through the water. Wait a minute, I thought that gas <-> liquid didn't
>happen in the bubbles!
No, just bubbling CO2 up thru the water will NOT result in any
increase in CO2 levels. There are several techniques used to help
dissolve the CO2 into the water.
One is a "co2 diffusor" which amounts to a VERY VERY VERY fine
airstone. Instead of getting bubbles coming out, you get an
incredibly fine mist of CO2. The CO2 mist does rise to the surface,
but most of these tiny CO2 bubbles will dissolve before reaching the
surface. The problem with a "co2 diffusor" is that the surface that
creates the mist gets dirty, and the bubble size increases, and the
amount of CO2 dissolving drops quickly.
A better method is to use a CO2 reactor. This is a tube where the
CO2 bubbles are trapped, and water flows past the CO2 bubbles, which
get churned around and dissolved. I believe this is also similar to
how a calcium reactor works.
>Furthermore, many powerheads have a venturi that lets you add bubbles to the
>output.
The air is being forced into a pressurized stream of water, which does
allow some O2 to go directly into the water. But most of the air
going into a powerhead will just rise to the surface, but that "rising
to the surface" helps O2 levels just like the airstone does, by
creating surface movement.
>surface motion provided by the powerhead all that's needed to provide
>aeration?
If you aim your powerhead under the surface of the water, you get
little or no surface movement due to the powerhead. A really
efficient way to get O2 into the water is to have the powerhead shoot
water up to the surface, or even slightly over the surface, to create
lots of surface movement or even a waterfall effect.
>Given the fact that my 4 Zebra Danios have been chasing each other happily
>around and have not been gasping at the surface for the last three days in
>my fully hooded tank, I think the "aeration doesn't happen in the bubbles"
>is a myth.
No, it just means that the normal water movement in your tank is
supplying enough O2 to keep your fish happy and healthy.
Chuck Gadd
http://www.csd.net/~cgadd/aqua
Marlin
tank, is contact time between the gas and the water. Hence the use of
reactors which increase the amount of time that a gas (O2 or CO2) is in
contact with the water. Fine bubbles also are a desired affect as they
travel slower through the water than a large bubble. Gasses are dissolving
and diffusing, but at what rate?
"Thomas Coon" <tc...@twcny.rr.com> wrote in message
news:ozXa7.187648$EF2.25...@typhoon.nyroc.rr.com...
Jimmy Chen
> increase in CO2 levels. There are several techniques used to help
> dissolve the CO2 into the water.
According to Craig B. personal observations, by just having a few more
guests in your house may generate enough CO2 to cause your tank's pH to
drop. It isnt that hard to have CO2 effecting your tank. No Ca reactor that
I know that are being sold on the reef hobby market does any special
treatment to CO2 other then a simple bubble injection, yet all of them can
get the pH down to 6.5 w/o problems.
> The air is being forced into a pressurized stream of water, which does
> allow some O2 to go directly into the water.
I hate to bring this point up, but with this whole series of posts, one
person indicated that O2 has a max level of 7ppm. I will agree that 7 ppm is
close to the max and 4ppm will means you have a totally dead system, and
even for FW system it is only around 11ppm or so. Has anyone even check what
the max CO2 level can be in a FW or SW system?
--
jc
Reefkeepers ML (http://www.reefkeepers.org)
Archived @ http://www.escribe.com/pets/reefkeepers/
Help Finding The Cure For Cancer
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0A9EEF2A8
Macbrush
before I replaced the substrate, replant everything and give off/throw away
at least 80% of the plants. Now, while the plants are recovering, and the
tank can only be considered medium planted, I still get well over 10mg/l
near the end of the day.
Previously, I kept CO2 up to 40ppm average without ill effect on anything.
Cheers
Kenneth
P.S. BTW, I have 300W 5200K HQI over a 36" 40 gal (US) tank. So don't go mad
on my figures. :-)
Jimmy Chen
So, logic says that even for an avg system, CO2 is at least 4x concentration
for a FW system compared to O2, then it isnt that hard to see why CO2 will
interact with h2o much easier then O2.
James Purchase
"Jimmy Chen" <jimmy...@nyc.rr.antispam> wrote in message
news:lI_a7.2011$l7.6...@typhoon.nyc.rr.com...
> > Previously, I kept CO2 up to 40ppm average without ill effect on
anything.
>
> So, logic says that even for an avg system, CO2 is at least 4x
concentration
> for a FW system compared to O2, then it isnt that hard to see why CO2 will
> interact with h2o much easier then O2.
Sorry, it isn't logic....at least not the way I think that your assuming it
works. In a planted FW tank with injected CO2, the levels of CO2 and O2 are
totally independent of one another and adding more of one doesn't mean that
the other one will go down.
Natural levels of CO2 in a clean aquarium (i.e. one with a clean mulm free
mineral substrate with no pockets of dead and decaying organic material)
that does not have CO2 injection would probably be in the range of 1-3 ppm.
CO2 is very soluable in water, but it leaves it just as fast as it enters
it.
Kenny's level of CO2 is maintained by injecting CO2 (at least I hope it
is...otherwise its one sick tank....lol). He's got over 7 Watts/gallon of
light over that baby and he NEEDS lots of CO2 because the light level is
pushing the system very fast. If he doesn't inject enough CO2 for the
plants, some of them will turn to the carbonate-bicarbonate buffer system
(the KH) and steal the CO2 they need from there.
It looks like his use of Aqua Soil is complicating matters as well but by
using some crushed shells and monitoring both his CO2 injection rate and
watching his KH (and adding baking soda as needed) he should be OK.
James Purchase
Toronto
Gremlin
dictated by a number of variables, to include temp, conductivity, barometric
pressure and partial pressure gradients. Once O2 gets to a certain level it
will diffuse into the atmosphere since its PO2/H2O pressure gradient is
higher than that of the air above, same for CO2.The standard PO2, @ 100mmHg
is .45 ml O2 / 100ml water and for CO2 it is 13.4 ml CO2/ 100ml water (or
CO2 is about 200 times more soluble) 22. 5 in water would be dangerous /kill
for aquatic animals. At 25oC, 1 atm, at equilibrium, O2 solubility is 8.32
mg/L (FW). ... you may get those high values e.g. 22.5 mg / l, right at the
plant water interface....but actual water level....no. Your talking greater
than 270 % saturation !!! . The solubility of *pure O2 is about 40 mg / l .
Who's test kit are you using that goes above 20 mg / l, most only go to 10,
15, or 20.....I think you are beyond the limits of the kit, or there is
something wrong with it or you application of it.
. Has anyone even check what
the max CO2 level can be in a FW or SW system?
I have somewhat jc, but there so many variables. There are formulas that can
be used. Also one needs to watch how they say things, e.g. NSW has about
<0.50 mg / l CO2 and the O2 is usually over 6. CO2 will be much higher in FW
and can reach into the 100's or more. Much of the CO2 that enters SW is
converted, so "actual" free CO2 ( what the kit is measuring, although a kit
used for testing SW won't work) is little, not the case with FW. In the
water world there is a value called Sigma CO2 or Ct, which means all the
free CO2_ and_ the HCO3, CO3 that can be converted into CO2.
'So, logic says that even for an avg system, CO2 is at least 4x
concentration
for a FW system compared to O2"
Not really, jc, only in a system that has reached complete equilibrium and
many closed systems don't, e.g. CO2 can leave the system/via plants faster
than it can diffuse from the atmosphere, thus the need for CO2 injection. CO
2 is controlled by the pH and ALK, if you know the pH and Alk you can
calculate the CO2, by Buch/Park equations. You could have a tank with 7 mg /
O2 and CO2 could be high or low and both at the same pH, temp,
conductivity and barometric pressure.
40ppm average ...isn't much of anything
Have you seen CO2/ALK/pH tables for FW Panted.......I can send you some if
you like, they show you the optimal levels for planted tanks
Tylent;
It is not a myth/say as the bubbles rise in the column there is diffusion
and the bubble water interface, where O2 leaves the bubble and CO2 enters,
but the amount of O2 is depend on a number of things, but really isn't all
that much.
"No, just bubbling CO2 up thru the water will NOT result in any
increase in CO2 levels"
This actually lowers the CO2, thus increaseing the pH
There are some nice posts here by Stare and Chuck
BOOMER
"Macbrush" <macb...@carriver.com> wrote in message
news:9khrph$4ig2h$1...@ID-86907.news.dfncis.de...
Jimmy Chen
> concentration
> > for a FW system compared to O2, then it isnt that hard to see why CO2
will
> > interact with h2o much easier then O2.
>
> Sorry, it isn't logic....at least not the way I think that your assuming
it
> works. In a planted FW tank with injected CO2, the levels of CO2 and O2
are
> totally independent of one another and adding more of one doesn't mean
that
> the other one will go down.
>
> Natural levels of CO2 in a clean aquarium (i.e. one with a clean mulm free
> mineral substrate with no pockets of dead and decaying organic material)
> that does not have CO2 injection would probably be in the range of 1-3
ppm.
> CO2 is very soluable in water, but it leaves it just as fast as it enters
> it.
I believe you misunderstood my meaning. In no form do I mean to say O2 and
CO2 are in portion in any FW/SW system. The main points I want to bring out
were ...
1. CO2, as someone indicated, is around 40ppm for FW. In breathing air I
believe its around 300 ppm.
2: O2 max is around 11ppm for FW and around 8ppm for SW.
3. In SW, even 4ppm of O2 will mean you have a dead tank because all of your
fish/corals/critters will be dead from lack of O2 at this low concentration.
4. Max supersaturating of O2 isnt that hard to achieve.
Now, put that all together, its easy to see why there is a lot less room for
O2 then CO2 to react to the waters.
Craig Bingman
Gremlin <gre...@the.cave> wrote:
>I don't believe your values of 22.5 O2 at all. O2 or CO2, in water, is
>dictated by a number of variables, to include temp, conductivity, barometric
>pressure and partial pressure gradients. Once O2 gets to a certain level it
>will diffuse into the atmosphere since its PO2/H2O pressure gradient is
>higher than that of the air above, same for CO2.The standard PO2, @ 100mmHg
>is .45 ml O2 / 100ml water and for CO2 it is 13.4 ml CO2/ 100ml water (or
>CO2 is about 200 times more soluble) 22. 5 in water would be dangerous /kill
>for aquatic animals. At 25oC, 1 atm, at equilibrium, O2 solubility is 8.32
>mg/L (FW). ... you may get those high values e.g. 22.5 mg / l, right at the
>plant water interface....but actual water level....no. Your talking greater
>than 270 % saturation !!! . The solubility of *pure O2 is about 40 mg / l .
So what gas do you think is forming bubbles on the surfaces of plants
when the system s highly driven by intense light?
If there isn't a lot of surface turbulence, then the system can go to
much higher than atmospheric pO2, because its rate of excape from the
system is kinetically limited. This limitation is either relaxed or
removed on CO2, since you have a way of getting it into the system that
doesn't involve exchange at the surface of the aquarium.
>Who's test kit are you using that goes above 20 mg / l, most only go to 10,
>15, or 20.....I think you are beyond the limits of the kit, or there is
>something wrong with it or you application of it.
If one uses a titration test for oxygen, there is essentially no upper
limit to the oxygen concentration that you can measure. You will start
to get errors at very high (or low) oxygen concentrations due to diffusion
of O2 into/out of the sample before the titration is complete. If 22.5
ppm is measured, my guess would be that the actual oxygen concentration
is somewhat higher than that.
I do think that this system is being pushed pretty darned hard. It might
be into a mode where it needs these extremely high pO2 levels during the
day, to prevent the system from going anoxic at night. I'd be a bit nervous
about it. My guess is that it is so far out there in parameter space
that it is highly susceptible to failure of a single-component.
As far as oxygen toxicity goes, humans and other terrestrial organisms
certainly don't immediately fall over dead in a 50% oxygen atmosphere
at 1 bar total pressure. There are definitely chronic consequneces,
but at this level, few if any organisms just fall over and die. That
is probably also true for most aquatic organisms as well. Especially
when one remembers that the dissolved oxygen concentrations in natural
waters can be far above "equilibrium" values when the systems are
brightly illuminated.
High carbon dioxide concentrations can protect photosynhetic organisms
against some, but not all consequences of very high oxygen concentrations.
There is a direct competition between oxygen and carbon dioxide at
the active site of rubisco, the keystone enzyme in the metabolic
pathway that fixes inorganic carbon in plants. Having plenty of
places to go with the reduced electrons from the photosystems also
helps prevent the photosystems from destroying themselves when brightly
illuminated.
Craig
Craig Bingman
Chuck Gadd <cg...@cfxc.com> wrote:
>On Sat, 4 Aug 2001 12:35:48 -0600, "Tylernt"
>No, just bubbling CO2 up thru the water will NOT result in any
>increase in CO2 levels.
That simply isn't true. I think what you meant to say was that
bubbling carbon dioxide through the water isn't the most efficient
way to get CO2 into the system.
Macbrush
that's before I thrown away most plants anyway. I think I will get back to
that kind of O2 level in about a month or two when plants are taking over
the tank again. Whenever I get an spectacular (abnormal) value, I always
carefully clean up everything, retest by the same kit, and then do it again
by another brand of test kit I have. Unfortunately, for O2 kit, I only have
Duplatest O2 (since its not important at all, I got it from a clearance sale
for fun), however, by the way the test was disgned and I've done it twice, I
am quite sure my results was correct. No, there is no upper limit with the
test kit, I've dropped Chemistry class as soon as I had the chance (second
form in college if my memory serve me right), so I have no idea what kind of
test it really is. It performs like this...
1. Carefully fill up the test tube to FULL, and I put the cap on it under
water.
2. Open the cap carefully, put 5 drops of solution A into the test tube.
3. Immediately put 5 drops of solution B into the test tube.
4. Leave the hole on the cap open, put the cap on, there will be excessive
water coming out from the hole, then close the cap.
5. Wait 10 mins, some kind of brown sediment will form. (If a large amount
of O2 is present, too much sediment will form, and one might need to lightly
banging the test tube against the palm to "COMPACT" them to bottom)
6. Make sure all visible brown sediment gets below 6ml mark, then drain
water out by openning the 6ml mark hole, gently and carefully.
7. Put 5 drops of solution C into the test tube, and let it sit for 5 mins.
8. Gently shake the test tube, and put enough drops of solution D (and count
the number of drops) until all sediment and colouration clear, leave only
with crystal clear solution.
9. Each number of drops of solution D represent 0.5 mg/l of O2.
I still remember that I got pearling almost immediately after lights on the
next day.
Cheers
Kenneth
"Gremlin" <gre...@the.cave> wrote in message
news:tmp6vsf...@corp.supernews.com...
Macbrush
any one value get out of normal range, everything else go crazy in the
system. I had two instances so far, in last fortnight.
Once the NO3 creeped above 10ppm (note that even PO4 was under 0.2ppm
average, around 0.5 after daily supplement), I immediately see green tint in
water within a few hours, luckily, a water change and 24 hr UV finished the
green thing nicely.
Another incident was after I filled the tank with new substrate, and didn't
realize it changes water parameter so dramatically, KH dropped from 7 to
almost 0 in just a few days. In order to prevent pH crash, I had to slowly
add bi-carbonate, and decrease the CO2 injection rate (I am still getting
help from here and APD on this issue). The problem is that I can't increase
KH too dramatically to prevent another shock to fishes, I have to keep under
fertilizing CO2 to maintain proper pH, under such low CO2 level (around
9ppm) decalcification occur in great effect bring down KH at a rate that
need daily attention, but I need to raise CO2 level to prevent further
decalcification. Oh... shoot... just thought of a solution (glad that I make
a reply to this post lead me to it)... *smile*, stop everything including
fertilizing and light, and leaving only CO2 on for a few days until I get
the KH right... YEAH!!! (actually, stupid me, should've thought of this a
long time ago)
Thanks pal! :-)
Kenneth
"Craig Bingman" <cbin...@panix.com> wrote in message
news:9kk6tp$gqh$1...@panix3.panix.com...
Boomer
Sorry Craig, but where did you come up with that, I never mentioned it ? I'm quite aware
of plants forming O2 bubbles. The discussion was on dissolved O2 in water. I did say "
22.5 mg / l, right at the plant water interface" Besides, a number of plants can be seen
with O2 bubbles, even in non-highly driven systems. You can get O2 bubbles under simple
florescent lamps.
Have you ever measure levels of O2 that high in a closed aquatic system ?
"If one uses a titration test for oxygen, there is essentially no upper
limit to the oxygen concentration that you can measure. "
OK, but what about the accuracy of his kit, since he just posted he bought it a clearance
sale and Dupla O2 kits were never that good or reliable, at least compared to the values I
got from a Hach digital titrator.
"As far as oxygen toxicity goes, humans and other terrestrial organisms
certainly don't immediately fall over dead in a 50% oxygen atmosphere
at 1 bar total pressure"
I never did either, but he is at 270 %, not 50 %, or am I missing something ?
In fish this can be considered toxic, as the water is for sure supersaturated with O2,
which can cause a massive distension of the swim bladder. The oxygen "loading" results in
overfilling the swim bladder, but mortality is usually low. At times it will get corrected
with "lights out". This just one example, I'm sure there are more.
"I do think that this system is being pushed pretty darned hard."
I would surely buy that if the numbers are real
"Especially
when one remembers that the dissolved oxygen concentrations in natural
waters can be far above "equilibrium" values when the systems are
brightly illuminated. "
Agreed, just like CO2 levels can go down to almost nothing, if not supplemented
"High carbon dioxide concentrations can protect photosynhetic organisms
against some, but not all consequences of very high oxygen concentrations."
There is a affect on some aquatic animals to include fish, which revolves around the Bohr
and Root effect and being able to respond to hypercapnic conditions.
Boomer
WCWing@Chartermi..net
If You See Me Running You Better Catch-Up
"Craig Bingman" <cbin...@panix.com> wrote in message
news:9kk6tp$gqh$1...@panix3.panix.com...
: In article <tmp6vsf...@corp.supernews.com>,
:
Boomer
find the number hard to buy. I have never seen anything that high. A friend of mine use to
run a heavily planted tank with CO2/ injection and it was no nowhere near that (22.5) I
did some checking and there appears to be no upper limit / say. How old is the kit and
when was the last time the reagents where replaced or is thee a date on them. Most should
be replaced every year and every two years for sure. It is pretty much standard practice.
Have you ever just check, say, just tap water ? Of course just because I have never seen
it doesn't mean may it couldn't be. Usually when one seems to say *can't or *never they
end up inserting foot in mouth...maybe I'm half way there ;-)
--
Boomer
WCWing@Chartermi..net
If You See Me Running You Better Catch-Up
"Macbrush" <macb...@carriver.com> wrote in message
news:9kkehl$4su4r$1...@ID-86907.news.dfncis.de...
: 22.5 is kind of record for me, I usually get around 16 - 18 in a normal day,
: > > >
: > > >
: > >
: >
: >
:
R. S. Pearce, Jr.
disagree with the snip below. I dissolve CO2 in water for my diy Ca reactor
by simply bubbling CO2, up through a column of water in an acrylic tube
(actually it was an old downdraft skimmer, about 18" tall). I do not use an
air stone to diffuse the bubbles, and they are quite large, but you can
actually see them shrinking as they rise through the water. I assume since
the bubbles are shrinking as they rise, and the pH of the water in the
column drops into the mid 6's (starting in the 8.2-8.4 range), that the CO2
is dissolving into the water.
"Chuck Gadd wrote ...
>snip>
Craig Bingman
Boomer <wcw...@chartermi.net> wrote:
>"So what gas do you think is forming bubbles on the surfaces of plants
>when the systems highly driven by intense light?"
>Sorry Craig, but where did you come up with that, I never mentioned it ? I'm quite aware
>of plants forming O2 bubbles. The discussion was on dissolved O2 in water. I did say "
>22.5 mg / l, right at the plant water interface" Besides, a number of plants can be seen
>with O2 bubbles, even in non-highly driven systems. You can get O2 bubbles under simple
>florescent lamps.
The point is that the plants are producing pure oxygen, and that the
partial pressure of oxygen can be substantially higher than one
would expect from the equilibrium values.
>Have you ever measure levels of O2 that high in a closed aquatic system ?
No, but I don't have a bazzillion watts of light over and itty bitty
planted tank that I have to pump boatloads of carbon dioxide into
to keep it from going into photosynthesis-induced decalcification.
One certainly reads tales of extremely high oxygen concentrations in
reef lagoons during maximumal illumination. I'm less familiar with
the literature on freshwater systems.
>"If one uses a titration test for oxygen, there is essentially no upper
>limit to the oxygen concentration that you can measure. "
>OK, but what about the accuracy of his kit, since he just posted he bought it a clearance
>sale and Dupla O2 kits were never that good or reliable, at least compared to the values I
>got from a Hach digital titrator.
Maybe the test kit is crap, maybe it isn't. It is fairly simple to get
a standard solution for an oxygen test kit. You just draw some tap
water, areate it adequately, and then read the expected oxygen concentration
from tabulated values.
Of course I suspect that very few people actually do that.
>"As far as oxygen toxicity goes, humans and other terrestrial organisms
>certainly don't immediately fall over dead in a 50% oxygen atmosphere
>at 1 bar total pressure"
>I never did either, but he is at 270 %, not 50 %, or am I missing something ?
No, he isn't at 2.7 bar oxygen partial pressure. His system is roughly 2.7x
the expected equilibrium concentration of oxygen dissolved in fresh water
at about that temp, which is roughly 0.5 bar oxygen partial pressure.
Boomer
--
Boomer
WCWing@Chartermi..net
If You See Me Running You Better Catch-Up
"Craig Bingman" <cbin...@panix.com> wrote in message
news:9kn7c4$caf$1...@panix3.panix.com...
: In article <tms1nm5...@corp.supernews.com>,
:
Macbrush
think he's right as information for aquarists. He meant it won't help just
bubbling CO2 with an normal airstone w/o additional equipment, and I agree
with this.
Cheers
Kenneth
"R. S. Pearce, Jr." <nospa...@bellatlantic.net> wrote in message
news:HMpb7.8079$AK6.2...@typhoon2.gnilink.net...