Gases are more soluble at lower water temperatures, with oxygen being the most commonly cited example of this in planted tank circles. However CO2 should follow this rule as well. If lowering an aquarium's water temperature (by a substantial amount, say 5 degrees Fahrenheit) - what should be done to the CO2 injection rate? Should it be decreased because the CO2 will be more soluble in water, or should it be kept the same because increased dissolved O2 will balance it out?
Keep the temperature best suited to the fauna you have in the tank and don't worry about the solubility of gasses being affected by temperature. The changes in solubility hardly matter for the purpose you use CO2.
This is what I'm looking to do; I started driving my canister filter w/ a new external pump and the heat from the pump has led to a tank temperature a few degrees higher than optimal for my inhabitants, so I am adjusting the heater to compensate and lower the temperature back down. Hopefully I won't have to tinker with my CO2 flowrate as a result.
If lowering an aquarium's water temperature (by a substantial amount, say 5 degrees Fahrenheit) - what should be done to the CO2 injection rate? Should it be decreased because the CO2 will be more soluble in water, or should it be kept the same because increased dissolved O2 will balance it out?
Under pH 6.7, KH 4, 20°C (68°F) you have 30 ppm CO2.
Under pH 6.7, KH 4, 25°C (77°F) you have 28 ppm CO2.
Under pH 6.7, KH 4, 30°C (86°F) you have 26 ppm CO2.
I think the differences are quite small to worry about.
Under pH 6.7, KH 4, 20°C (68°F) you have 30 ppm CO2.
Under pH 6.7, KH 4, 25°C (77°F) you have 28 ppm CO2.
Under pH 6.7, KH 4, 30°C (86°F) you have 26 ppm CO2.
I think the differences are quite small to worry about.
What if the temperature in my 65 gal planted aquarium is 85 degrees but my ph is 7.6 and my KH is 4? I am running a 5lb CO2 tank and diffusing it through my 350 gph power-head 6bps.
I was looking more for "relative" changes so it wasn't critical.. but this is a reference:
But carbon dioxide is relatively insoluble in water exposed to the atmosphere, being theoretically soluble to the extent of only 0.5 ppm at 20°C, and 1.0 ppm at O°C as shown on Fig. 57.
Solubility, X_1, of CO2 in water.
Handbook of Chemistry & Physics,
34th ed., 1953, Solubility of Gases
in Water, p. 1532. The curve is the
best–fit, fifth order by the author.
Above is where the odd charts from
X_1 is just a symbol or notation apparently
Molar solubility.. Don't ask me.. How to Calculate Solubilities | Sciencing
Best I can guess is grams CO2/100G of water..
Seems an archaic term to me..
Like this only multiplied by 10 (kg of water)
If you can see the teenie tiny numbers on the right (0-1ppm CO2)
Can't believe I can't find a decent chart..
20C 68F .5ppm (sat), 30C 86F .4ppm (sat)
As to the CO I could pretend it was just to show O2 but actually it was just an oppsie..
28.01g/mole CO
.02801g/L
Thanks, the reason I am asking is I read somewhere (I think the krib) that at equilibrium under atmospheric pressure co2 concentration will be 2-3 ppm so that leaves a lot of room for difference in the interpretation of measuring Co2 and was trying figure a way to be more accurate about my specific location, temp etc. If its only 2ppm then at 1.2 PH drop that would be 32 ppm and if it was 3ppm at 1.2 PH drop then it would be 48ppm. A bit of a difference.
Well the solubility has been covered, but the flux is also important. At higher temps, wont plants metabolize CO2 faster? You will also evaporate CO2 slightly faster. This means any drop in solubility is probably made up for needing to add more to maintain the same concentration.
@osmosis I hate you for understanding all this stuff. The chemical reaction side of things in this hobby drive me nuts to no end trying to understand it. I am honestly considering taking some courses to get a minor grasp.
Atmospheric replacement also comes into play..
As CO2 is depleted it will drive more atm CO2 into solution..
Obviously replacement can easily be exceeded by fast depletion..or injection would not be necessary..
Then there is diffusion..
Point is its a dynamic situation w/ multiple parameters and sinks..
I wondered if someone would be so kind as to explain ATM in reference to A Planted Tank. I only know of two. ATM = At the moment or Automated Teller Machine.
ATM one atmosphere of pressure..at sea level I believe.
14.70 pounds per square inch
Standard sea-level pressure, by definition, equals 760 mm (29.92 inches) of mercury, 14.70 pounds per square inch, 1,013.25 × 10 3 dynes per square centimetre, 1,013.25 millibars, one standard atmosphere, or 101.325 kilopascals.Apr 19, 2017
just used to define a standard condition.. and to avoid confusion of conditions. Solubility for most things change w/ increasing pressures..
Why beer releases gas when opened..
I'm just gonna sit here and wave to the people out the back window of the short bus. By the way I'm taking the names of you chemists out there for future questions, my gain your loss.
Sits next to Dan and waves to them'ns that unnerstands *stuff*. We'll get 'em pal just wait n see!
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