# co2/kh, psi



## anubias6439 (Sep 7, 2010)

-for those of you with pressurized co2 systems- kh. At what levels do you keep it? i understand there is a relationship between ph, kh and co2. the current readings in my tank are kh-7, ph 7.2. those reading are six days since the last water change. the tap water reads kh-9, ph 7.2. very similar to my tank. as of now, i do not have pressurized co2 but i did order a system from greenleefaquariums yesterday. will my kh level be ok/safe for the addition of co2? will the kh drop after co2 is introduced and will i need to add baking soda and/or crushed sea shells if this happens?
-pressure on co2 cylinders- do the distributors by default fill them to 800 psi? i believe this is the pressure that should be coming out of the tank and into the regulator to be adjusted down to 10psi for aquarium use. if the pressure is always 800 psi when they fill them, i have no questions. sooooooo, if it isnt, and say they fill it to 2000 psi or whatever, (i read that you need to open your valve on the cylender the whole way or leaking may occur), how do you get away with this?


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## ray-the-pilot (May 14, 2008)

anubias6439 said:


> -for those of you with pressurized co2 systems- kh. At what levels do you keep it? i understand there is a relationship between ph, kh and co2.
> 
> -pressure on co2 cylinders- do the distributors by default fill them to 800 psi? i believe this is the pressure that should be coming out of the tank and into the regulator to be adjusted down to 10psi for aquarium use. if the pressure is always 800 psi when they fill them, i have no questions. sooooooo, if it isnt, and say they fill it to 2000 psi or whatever,


Question 1: Are you getting a CO2 controller or are you just winging it? It makes a difference?

Question 2: You don't buy CO2 by psi you buy it by pounds. 
CO2 is a liquid and they fill your tank just like your propane tank until the weight is just right. The pressure you read on the gauge is the vapor pressure of liquid CO2 at the temperature of the tank so it is pretty much constant until the tank runs out. If the gauge reads 2000 psi the tank has to be really hot and I get away from it fast.


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## anubias6439 (Sep 7, 2010)

> Are you getting a CO2 controller or are you just winging it?


it will be a system from green leaf aquariums with the included controller. My question was about kh


> It makes a difference?


what makes a difference?


> Question 2: You don't buy CO2 by psi you buy it by pounds.
> CO2 is a liquid and they fill your tank just like your propane tank until the weight is just right. The pressure you read on the gauge is the vapor pressure of liquid CO2 at the temperature of the tank so it is pretty much constant until the tank runs out. If the gauge reads 2000 psi the tank has to be really hot and I get away from it fast.


i understand the psi vs. weight. i have a ten pound tank on order. is the psi always going to be 800 for a fully turned on valve?


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## Skizhx (Oct 12, 2010)

A lot of people don't bother screwing around with their PH and KH and just use their tap water as is.

If you must know, I have 3dKH in my water, and my PH (in the aquarium with CO2 running) is about 6.4. But this is by no means something I aimed for. It's just how my water is...

If you're trying to determine how much CO2 is in your water by the PH, you may find it easier to just use a drop checker. These are fairly cheap, and fairly simple to use.


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## anubias6439 (Sep 7, 2010)

alright, i actually have a drop checker ordered also. will the co2 injection make the kh drop in an aquarium?


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## JeffyFunk (Apr 6, 2006)

anubias6439 said:


> -for those of you with pressurized co2 systems- kh. At what levels do you keep it? i understand there is a relationship between ph, kh and co2.


The kH of your system will determine how much CO2 it takes to reduce the pH value of the solution by 0.1 scientific units. If you do a quick google search, you can find out how much CO2 is in solution by knowing the pH & kH of your aquarium. (Disclaimer - I don't use a pH controller for my pressurized CO2). If you use a pH controller for your pressurized CO2, you should watch the behavior of your fish to determine what pH value to set your pH controller. If your CO2 concentration is too high, you'll see your fish gasping and/or shrimp acting funny. To "accurately" determine the CO2 concentration, most people use a drop checker. A drop checker is a solution of known kH value (usually 4.0) w/ a pH indicator solution in it (Bromothymol blue (sp?)). When the CO2 concentration of your aquarium is "low", the color of the drop checker will be blue (because the pH of the indicator solution is too high). When the CO2 concentration of your aquarium is "ideal", the color of the drop checker will be green. When the CO2 concentration of your aquarium is "high", the color of the drop checker will be yellow (because the pH of the indicator solution is too low). And no, CO2 will not affect your kH.



anubias6439 said:


> -pressure on co2 cylinders- do the distributors by default fill them to 800 psi


As Ray said, CO2 cylinders are filled by weight. At standard temperature and pressure (STP), CO2 is a gas. When you increase the pressure of CO2 (as in a tank) at standard temperature, eventually the CO2 will form an equilibrium between a liquid and a gas. As more CO2 is then added to the tank, the pressure of the CO2 will remain the same because that additional CO2 will turn into a liquid (liquids have negligible pressure). That is why the CO2 cylinders always read ~800 psi.

The only time the CO2 cylinder will not read ~800 psi is when the tank is getting empty. As long as there is liquid CO2 in your tank, then some of that liquid CO2 will become gaseous CO2 as the CO2 is used up, keeping the tank @ ~800 psi. When the tank is almost empty, however, there will no longer be any liquid CO2 in the tank and so the pressure of the tank will drop (pretty quickly in fact).



anubias6439 said:


> i believe this is the pressure that should be coming out of the tank and into the regulator to be adjusted down to 10psi for aquarium use.


Also, the pressure is not necessarily adjusted down to 10 psi. The pressure is adjusted down to whatever pressure is needed to operate your needle value. For example, I have bought two different CO2 regulators from Greenleafaquariums.com, each w/ a different needle value (Their choice & primo CO2 regulators). I've noticed that the primo CO2 needle value needs a higher outlet pressure of >20 psi in order to work properly while the choice CO2 needle values does not require as high of an outlet pressure.



anubias6439 said:


> sooooooo, if it isnt, and say they fill it to 2000 psi or whatever, (i read that you need to open your valve on the cylender the whole way or leaking may occur), how do you get away with this?


This question makes no sense to me; It's impossible to fill it up to 2000 psi @ standard temperature. (Maybe at an elevated temperature, but i'd also run away as Ray said).


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## anubias6439 (Sep 7, 2010)

thank you. it all makes sense now.


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## jerrybforl (Jul 22, 2008)

You want your KH and GH between 3 and 6. You can roughly determine your CO2 count on a chart that you can find online that crosses your ph with your KH. where ever they cross thats your 
CO2 count. I use RO water with Seachems Alkaline and Acid buffer ratio to get the KH that I want. and Equilibrium to put in the amount of nutrients that I need for the water and such. I live in south Fl and our water is very unstable so thats why I use RO. Hope this helps..


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## ray-the-pilot (May 14, 2008)

anubias6439 said:


> alright, i actually have a drop checker ordered also. will the co2 injection make the kh drop in an aquarium?


Yes you need a drop checker but do you have a CO2 controller (some people call it a pH controller)?

Also, do you have a solenoid valve, needle valve, and what kind of regulator?

By definiton, no matter how much CO2 you add, the KH wll not change.


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## ray-the-pilot (May 14, 2008)

anubias6439 said:


> it will be a system from green leaf aquariums with the included controller. My question was about kh
> 
> what makes a difference?


Here is the issue. A CO2 controller is like a heating system with a thermostat. A bubble counter is like a wood burning stove. Both will heat your house and both will keep you from freezing in the winter. Both will help you grow plants.

The KH question is important depending on which system you use.


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## anubias6439 (Sep 7, 2010)

jerrybforl said:


> You want your KH and GH between 3 and 6. You can roughly determine your CO2 count on a chart that you can find online that crosses your ph with your KH. where ever they cross thats your
> CO2 count. I use RO water with Seachems Alkaline and Acid buffer ratio to get the KH that I want. and Equilibrium to put in the amount of nutrients that I need for the water and such. I live in south Fl and our water is very unstable so thats why I use RO. Hope this helps..


yes i have become very familiar with these charts in the past couple of days. i actually have acid buffer on hand but i think i will see how the system does the first week or two before i change water paremeters too much


> Yes you need a drop checker but do you have a CO2 controller (some people call it a pH controller)?
> 
> Also, do you have a solenoid valve, needle valve, and what kind of regulator?
> 
> By definiton, no matter how much CO2 you add, the KH wll not change.


i was told drop checkers are not needed, however, i am getting one as i am curious and want to get this right. 
you seem to have lots of questions about my co2 setup so here it is
29 gallon tank
Milwaukee SMS122 pH controller
10 LB CO2 cylinder
Brass check valve
choice co2 regulator, information about it can be found here http://www.greenleafaquariums.com/complete-co2-systems/choice-co2-system.html
plus as i said before, i did order a bubble counter and a diffusor with the complete choice ssystem. i was told in the equipment forum here that this company sells fine co2 systems.


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