betowess
Aquarium Advice Freak
I'm glad I don't swim in that tank. Seems a little cruel to the fins. I'd get a hagen and give it a little time.
dry ice
- Thread starter Dr.Danio
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C
cj10488
Guest
Dry Ice should be availible at Ice Cream shops as well as some grocery stores.. Well at least around here it is
I am pretty sure that It is pure Co2 but not 100%
If it were me I would say no more than a 1/4lb..
FWIW It usually sells for about 5.00lb here and you can only really buy what you are going to use the same day as we as consumers do not have the proper way of storing it..
However for a more scientific way to dose it would be get a Plastic 2 liter and drop some dry ice into about 1 liter of water.. Place a cork with an airline in it or a garden hose and let the Co2 run into the tank on a slower basis.. make sure air can flow out of the bottle real easy otherwise ya might get hurt..
James
MantisX
Aquarium Advice Activist
I dont understand. Is this dry ice idea supposed to be cheaper than DIY or is it just something to try?
C
cj10488
Guest
Cheap easy experimenting way about introducing co2 into a FW planted tank..
James
G
Guest
Guest
If one wanted to kick start an new aquarium with no fish in in why not just use a pressurized system and turn up the bubble rate? That way you have a constant supply of high levels of CO2.
G
Guest
Guest
Let me think. A 1 gram piece in a 10 gallon tank caused a 1 point pH drop. And you think that ~113 grams is going to work well in a 50 gallon tank? Wow!
jsoong
Aquarium Advice Addict
The thing I am getting out of this experimentation is that the CO2 is staying in the tank for so long. I would have expected to see the CO2 disappearing within minutes, what with water movement & all.
*If* the CO2 is truely staying for hours after a single dose, then a pulse delivery system of CO2 is possible. Also, I must then also question the conventional wisdom of having no water surface aggitation in CO2 injection systems. If CO2 takes that long to come out of solution (with a high concentration gradient to boot), then what is a little water movement?
cj - if you are going to the trouble of putting the dry ice in a bottle & setting up a continuous flow system, why not just use regular pressurized CO2? At $5 a lb, dry ice gets expensive pretty quick, esp. when you have to get a new supply everyday. Once you get the CO2 tank, getting a refill is pretty cheap.
*If* the CO2 is truely staying for hours after a single dose, then a pulse delivery system of CO2 is possible. Also, I must then also question the conventional wisdom of having no water surface aggitation in CO2 injection systems. If CO2 takes that long to come out of solution (with a high concentration gradient to boot), then what is a little water movement?
cj - if you are going to the trouble of putting the dry ice in a bottle & setting up a continuous flow system, why not just use regular pressurized CO2? At $5 a lb, dry ice gets expensive pretty quick, esp. when you have to get a new supply everyday. Once you get the CO2 tank, getting a refill is pretty cheap.
G
Guest
Guest
But the one factor that we don't know is the kH of the tank you are playing with.
lbritish
Aquarium Advice Apprentice
personally I'd look more toward trying to harness it like DIY CO2 in a soda bottle situations... put the dry ice in a container with a tube going from it to a difuser and w/ counter current etc... since after all it IS CO2 in solid form... then it melts and turns gaseous... this way you harness the CO2 longer since a single chunk of dry ice roughly candy bar sized will last several hours w/o insulation. Something about red brick sized lasts a little over 1-2 days if inside a foam insulated container...
BUT.. I dont know the release rates... when you place it directly in water alot of it bubbles to the surface and not get absorbed into the water... so if you had a counter current reactor against the piece put in you'd see a much larger pH shift... and also more CO2 in the water.
Another point was you started off with water we dont know any of the properties of.. specifically KH... if it was 0 KH and you tossed the piece in it would certainly shift quickly... but if you had a KH around 10 which may be more normal in a CO2 injection system for what people would probably use to maintain efficient use of the CO2 it might not shift as fast..
Anyway.... I'd think you'd want to get some sorta small container that is sealed with a tube coming out into a classic co2 reactor or diffuser instead of just dunking it straight into the tank... then bubbling off 80% of your CO2 and burning out the supply in 10 minutes or less...
then you have the options of controlling the conversion from solid to gas by room temp, insulation, or providing a heat source through various methods...
vs... PLOP Woooooooooo look at it go..... YEAH!!!! BUBBLE BUBBLE....wait... oh..darn.. it's melted already.....
BUT.. I dont know the release rates... when you place it directly in water alot of it bubbles to the surface and not get absorbed into the water... so if you had a counter current reactor against the piece put in you'd see a much larger pH shift... and also more CO2 in the water.
Another point was you started off with water we dont know any of the properties of.. specifically KH... if it was 0 KH and you tossed the piece in it would certainly shift quickly... but if you had a KH around 10 which may be more normal in a CO2 injection system for what people would probably use to maintain efficient use of the CO2 it might not shift as fast..
Anyway.... I'd think you'd want to get some sorta small container that is sealed with a tube coming out into a classic co2 reactor or diffuser instead of just dunking it straight into the tank... then bubbling off 80% of your CO2 and burning out the supply in 10 minutes or less...
then you have the options of controlling the conversion from solid to gas by room temp, insulation, or providing a heat source through various methods...
vs... PLOP Woooooooooo look at it go..... YEAH!!!! BUBBLE BUBBLE....wait... oh..darn.. it's melted already.....
jsoong
Aquarium Advice Addict
Read here & a few places that KH will buffer pH change with CO2 injection. This is not true.
KH is measuring your HCO3- level. HCO3 will buffer when you add additional acids by reacting with the H+ & form CO2. Then CO2 then disappear into air, in effect, removing the H+.
When you add CO2 however, the H+ is created because excess CO2 is in the system & you are shifting the equilibrium point toward the acidic side. In this case, all the HCO3- in the world won't help you, because it cannot react to form more CO2.
Also, we know the KH in the tank... Using the Henderson Hasselbach equation, you can solve for the HCO3- level, given the starting pH of 6.0 and atmospheric CO2 level. In this case the HCO3- level is very low - KH being less than 0.25.
KH is measuring your HCO3- level. HCO3 will buffer when you add additional acids by reacting with the H+ & form CO2. Then CO2 then disappear into air, in effect, removing the H+.
When you add CO2 however, the H+ is created because excess CO2 is in the system & you are shifting the equilibrium point toward the acidic side. In this case, all the HCO3- in the world won't help you, because it cannot react to form more CO2.
Also, we know the KH in the tank... Using the Henderson Hasselbach equation, you can solve for the HCO3- level, given the starting pH of 6.0 and atmospheric CO2 level. In this case the HCO3- level is very low - KH being less than 0.25.
G
Guest
Guest
jsoong,
I think you are wrong in your assumptions. kH will buffer you from pH changes. The more kH you have in a tank the more CO2 it will take to drop the pH.
I think you are wrong in your assumptions. kH will buffer you from pH changes. The more kH you have in a tank the more CO2 it will take to drop the pH.
jsoong
Aquarium Advice Addict
Hmm .. May be I am not understanding this correctly ...
My reasoning is this:
1. Almost all CO2 in your tank is in dissolved form.
2. Almost all dissolved CO2 is reacted to form HCO3- & H+. There is very little "free" CO2 in water.
So, ignoring the small amount of free CO2, I can say:
For each molecule of CO2 dissolved in the tank, there is 1 extra molecule of H+ created.
Therefore, for any amount of CO2 that *stays in the tank*, there is a fixed increased in [H+], and a corresponding (fixed) drop in pH.
It is true that as the [HCO3-] increases, less CO2 will react to form HCO3- & H+ (as per the Henderson Hasselbach equation). But as the amount of free CO2 carried in the water is limited, any unreacted CO2 will simply disappear (into air).
So the way I understand it is - The higher the KH, the more CO2 you need to add to drop the pH. But for each unit of pH drop, a set additional amount of CO2 has been added to the tank. This amount is the sum of the "CO2 level" (the free, dissolved but unreacted CO2), and the increase in KH (the reacted form of CO2).
The HCO3, then is not buffering the pH change. Presence of high KH means you just have to add more CO2 to acheive a desired increase in tank CO2 level.
Make sense? or am I missing something.
My reasoning is this:
1. Almost all CO2 in your tank is in dissolved form.
2. Almost all dissolved CO2 is reacted to form HCO3- & H+. There is very little "free" CO2 in water.
So, ignoring the small amount of free CO2, I can say:
For each molecule of CO2 dissolved in the tank, there is 1 extra molecule of H+ created.
Therefore, for any amount of CO2 that *stays in the tank*, there is a fixed increased in [H+], and a corresponding (fixed) drop in pH.
It is true that as the [HCO3-] increases, less CO2 will react to form HCO3- & H+ (as per the Henderson Hasselbach equation). But as the amount of free CO2 carried in the water is limited, any unreacted CO2 will simply disappear (into air).
So the way I understand it is - The higher the KH, the more CO2 you need to add to drop the pH. But for each unit of pH drop, a set additional amount of CO2 has been added to the tank. This amount is the sum of the "CO2 level" (the free, dissolved but unreacted CO2), and the increase in KH (the reacted form of CO2).
The HCO3, then is not buffering the pH change. Presence of high KH means you just have to add more CO2 to acheive a desired increase in tank CO2 level.
Make sense? or am I missing something.
G
Guest
Guest
I'm having a hard time following your logic. It's true that the CO2 in the tank does form HCO3. And the HCO3 doesn't buffer the water the bicarbonates do. But the way I see it you figure that injecting CO2 is going to cause a large drop in kH. And it doesn't.
ok, back to work on monday. wow, alot or replies... nice
first things first..
DO NOT PUT DRY ICE IN A SEALED CONTAINER that is unless you want an explosion. seriously, the ppl that talk about DI bombs are right.
more about the chemistry and a few more experiments after class.
first things first..
DO NOT PUT DRY ICE IN A SEALED CONTAINER that is unless you want an explosion. seriously, the ppl that talk about DI bombs are right.
more about the chemistry and a few more experiments after class.
jsoong
Aquarium Advice Addict
Rex Grigg said:
OK - HCO3- IS bicarbonates, which in the absence of added buffer (like pH down, etc.) is what KH is measuring. So perhaps I should say - in the absence of other buffers, having high KH will not buffer against pH drop in CO2 injection?
No - I did not figure that injection of CO2 will drop KH. CO2 forms HCO3-, so should increase the KH. BUT CO2 injection will drop the pH.
Actually, I've been thinking on this some more. Perhaps, I should not have ignored the small unreacted CO2. After all, the end point of CO2 injection is raising the free CO2, right? In that case, the presence of HCO3 in the tank will decrease the reaction of CO2 to HCO3, so you need to add less CO2 to achieve your end point, and hence have less of a pH drop.
Maybe this is a better explanation of the observations?
PS - From all this talk, you might think I am a theoretician. Well, I do love theoretical stuff, but theory is nothing without emperical proof. Perhaps Dr. D can repeat the dry ice experiment (using just water, NO fish!
). If you can measure the actual CO2 level change over time, in addition to pH, that would give the definitive answer.lbritish
Aquarium Advice Apprentice
Dr.Danio said:
and to clarify my statement earlier.... when I said put it in a container with a tube going into a difuser or other reactor system... I meant literally that... a vented opening for the pressure to escape through...
it must have the ability to get out unrestricted... difuser not suggested... reactor where it has a counter current bubble much more suggested...
but as pointed out earlier... only suggested if you got a really cheap supply of dry ice like you work next door to a ice cream store that uses it to ship ice cream that you can pick it up from or something like that... (have lots of schwanns frozen food delivered via mail? something?)
