Old school co2 method.

tiger15

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I was more aiming my arrows on this, since i live close to the border i have a German delivery address, no international shipping cost as local a pic up. :)
https://www.ebay.de/itm/Kohlensaure...910803?hash=item56b2338ed3:g:468AAOSwX0xbPEIq



Probably, i'm not into the mater enough to say something conclusive about it.. As said each 10mm down is a 0.0001 bar pressure buld up. If you can speak of a pressure increas, relatively.. I have no idea on the numbers of the force needed for co2 compresion as in boyls law. There obviously will be a form of counter pressure by the gas. I would need to dig realy hard for numbers and formulas. To calculate which force is the greatest.

For now obviously the upwards pressure on the co2 in the vacum is 1 atmosphere. If the level of co2 is 15cm bellow the surface it will be 1.0015 atmosphere.. I guess the whole only can be theoreticaly calculated without an accurate barometer measuring the invironmental air pressure which next to that never is constant. Without it we assume it is 1.. If it isn't you always will be a few 1/10000 units off.

Neglecable if you ask me.. If it wasn't we didn't use 1 as a starting point for calculation. :) And an atmosphere pressure sensor would be common tool as must have.

Your estimate is too simplistic and can't be correct. When you open a can of soda, CO2 bubbles are released due to reduced pressure. CO2 is under slight pressure in the can, probably no more than at the bottom of a fish tank for safety concern.

Boyls law defines the relationship of gas pressure and volume. It's a universal law applicable to all gasses. The relationship of CO2 solubility and pressure is governed by the properties of specific gas (CO2 in this case) that vary from gas to gas. There are also other influencing factors such as temperature, partial pressure of CO2, and concentration gradient at the air water interface. It's complicated and the only sure way is to figure out is to conduct experiments to compare CO2 concentrations under different depths.
 

zozo

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Your estimate is too simplistic and can't be correct.

I actualy have no clue which estimate i made you are refering to.. The estimate that water presure in an aqaurium is neglectable because it is so little to make a fuss about it? I guess it must be that one i didn't made another estimate in that comment. :) And concerning this i hold my ground that it is in relation to the whole Co2 concept as we practice it in the hobby.. It is overall based upon estimates, as for example the dropcheckers color or the use of the Ph/kH profile chart. :)
 

tiger15

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. The estimate that water presure in an aqaurium is neglectable because it is so little to make a fuss about it? :)
When you say there is negligible pressure difference in a fish tank, it implies there is negligible impact on CO2 solubility so why make a fuss about it. You don’t know until you do a pH profile check on the impact.
 

zozo

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When you say there is negligible pressure difference in a fish tank, it implies there is negligible impact on CO2 solubility so why make a fuss about it. You don’t know until you do a pH profile check on the impact.

It probably has an minor impact on co2 solubilty, but it will be very minimal in an aquarium.. And since we are talking fractions of 1/10000, it is percentages of milibars and is indeed is nitpicking. Then suppose i submerse a bottle in my test object which is barely larger than the bottle height i can't submerse it completely without the open side of the bottle toughing the substrate.

Anyway since the atmospheric pressure on the tanks surface water has influence on the natural watercolumn pressure i have no way to tell what i'm looking at without a very accurate barometer. Since depending on this condition in between weather fronts can have a differnce of 100mm/millibar pressure difference i also have this pressure differnce bellow the water surface a few cm bellow it. Than the pH profile doesn't tell me much, becuase the pressure doesn't have a constant. The fluctuating atmospheric pressure on he water surface can be greater than the static very tiny watercolumn pressure in the tank. Thus it fluctuates.. Than it would be needed to monitor both and track it a rather long periode and make an average to be conclusive. Be my geust and put it to the test, you might find out that in cold days the co2 solubility is greater than in warm days. It probably is in average always with a few ppm, also when we use other means than this old school co² method.

That is not an estimate but i physical fact we can not get around and i don't like to dispute about because it is to far out off the workings of my brain..

And since we have no hobby means to determine this with very concusive numbers we all just stop at looking at a drop checkers color or at a pH profile. If it's green it's good enough for <Henderson–Hasselbalch> :crazy: than it must be good enough for me.. And it is. :thumbup:
 
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zozo

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And read back @Marc Davis comment, he has a bottle submersed with the same amount of co2 in it and he has to refill it in the same rate as a bottle Emersed with a vacuum.. Why should i test that agian.. He answered the qeustion that is fairly the same in both way the bottles are equaly empty in the same time.. If it was so much beter he would need to refill iit more often, since he doesn't.. Why should i try again what he is doing and say "Yes you are correct".. That's what's called trying to reinvent the wheel.. :)
 

tiger15

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And read back @Marc Davis comment, he has a bottle submersed with the same amount of co2 in it and he has to refill it in the same rate as a bottle Emersed with a vacuum.. Why should i test that agian.. He answered the qeustion that is fairly the same in both way the bottles are equaly empty in the same time.. If it was so much beter he would need to refill iit more often, since he doesn't.. Why should i try again what he is doing and say "Yes you are correct".. That's what's called trying to reinvent the wheel.. :)
You can’t go by frequency of refilling, as the density of co2 submerged is higher than emerged. So more co2 mass is filled submerged than emerged. Onlly pH comparison can tell the difference assuming you have a high resolution pH meter, and that you submerge all the way to the bottom of a deep tank. Submerging just beneath the surface or to the bottom of a shallow tank will not likely show any measurable difference. This is evident when you use an air stone, as the bubbles expand as they rise due to reducing pressure following Boyd’s law.
 

zozo

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You can’t go by frequency of refilling, as the density of co2 submerged is higher than emerged. So more co2 mass is filled submerged than emerged. Onlly pH comparison can tell the difference assuming you have a high resolution pH meter, and that you submerge all the way to the bottom of a deep tank. Submerging just beneath the surface or to the bottom of a shallow tank will not likely show any measurable difference. This is evident when you use an air stone, as the bubbles expand as they rise due to reducing pressure following Boyd’s law.
Finaly you got me there!!!.... :thumbup:;) I admit you are absolutely right.. 0.0015 extra atmosphere compresses the co² so you get more of it in the same volume... You are correct.. And i don't know how and also don't want to put the energy in it to calculate how much..
You may do that for us.. Or maybe you know already, but are not telling just to keep the exitement up.. :rolleyes:
 

ian_m

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This is evident when you use an air stone, as the bubbles expand as they rise due to reducing pressure following Boyd’s law.
This got me pondering, there is now way this can be true. Bubbles do not change volume due to Boyles law in rising up a fish tank, it is way way not deep enough to have any visible effect.

Boyles law states Pressure times volume (PV = k) is a constant for a gas at fixed temperature.

Thus at top of tank for a bubble of volume V(top) -> P(top) x V(top) = k.
Similarly at bottom P(bot) x V(bot) = k.

Thus P(top) x V(top) = P(bot) x V(bot)

If pressure at top of tank is 1 atmosphere, pressure at bottom for 50cm (0.5m) tank will be 1 atmosphere + (0.5 m / 10m) -> 1.05 atmospheres. (10m of water adds 1 atmosphere).

Volume of spherical bubble is 3/4 π R^3. (R = radius).

If we assume a bottom bubble radius of 1mm and ignoring the 3/4 π bit (as both sides of the equation) you get

R(top)^3 = R(bot)^3 x 1.05.

Take cube root.

R(top) = 1.016mm.

Hardly a big increase in radius !!! A 5% increase in volume.

However, you will perceive an increase in size as often the bubbles do not stay spherical but flatten out into saucer shapes.

Slightly different with a fizzy drink as the rising CO2 bubbles pick up more gas as they rise.
 

zozo

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If pressure at top of tank is 1 atmosphere, pressure at bottom for 50cm (0.5m) tank will be 1 atmosphere + (0.5 m / 10m) -> 1.05 atmospheres. (10m of water adds 1 atmosphere).

In all excitment i added a 0 to much. Since 1 cm water column is 1/1000 bar.. Proofs i'm getting to old for this cr*p? :rolleyes: Only tried to explain that as long as we keep 1 atmosphere as average starting point and don't measure the true present atmospheric pressure than the aqaurium depth or its water culomn pressure is neglectable. Because you might have 1050 millibar at this location and 970 millibar atmospheric presure at a different location at the same time.

That difference in atmospheric pressure covers about every normal household aquarium size. So 99% you might just always be slightly incorrect in such a nitpick calculation. But it doesn't seem to sink in. Mean while i'm wondering myself why the hell am i trying to explain this after all.. :crazy: I give up..
 

cheekycharly

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Got to this post after being amazed at the same video from aquarium co op. Has anyone found a well presented co2 chamber like the tropica one but a bit larger as I was going to try this on my 180L Rio that has no Co2 currently and do before and after.
 

Cheltster

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. Marc was that just with the Tropica Co2 diffuser in the corner or did you add liquid carbon or go full FE?

I have total tank envy BTW.
 

Marc Davis

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Wow that turned out amazingly! Was this just with the tropica kit? What else are you using?

Just some chelated trace elements (tropica premium). I never use NPK in my tanks. Just causes algae everywhere (i know lots dont agree with this, but ive witnessed it loads of times now)

It also has 2x led 20w floodlight lamps from Homebase. thats it.

After the co2 canister ran out from the tropica kit, i just made my own co2 with sugar and yeast and have been ever since.

Here is the tank now, went for a nature aquarium look rather than dutch:

20190110_131740.jpg
 

Zedan

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Just some chelated trace elements (tropica premium). I never use NPK in my tanks. Just causes algae everywhere (i know lots dont agree with this, but ive witnessed it loads of times now)

It also has 2x led 20w floodlight lamps from Homebase. thats it.

After the co2 canister ran out from the tropica kit, i just made my own co2 with sugar and yeast and have been ever since.

Here is the tank now, went for a nature aquarium look rather than dutch:

View attachment 121329

Love it! What are your thoughts on the tropica kit, would you recommend it?
 

Marc Davis

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Love it! What are your thoughts on the tropica kit, would you recommend it?
yes def. I still use the co2 bell to collect my diy co2. It is nice and compact with clear suckers that full secure it to the aquarium. i keep it at the back hidden by plants. I dont really understand why anyone would do a planted tank with at least diy co2. The difference between having it and no co2 is night and day.
 

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