# How long should a 10# tank of co2 last?



## steel1212 (Feb 21, 2006)

I just replaced one of my 10#ers on my 75 and I'm pretty sure I only had it going since oct. I have it running through a t valve to 2 wood stones. It is open pretty good to get the co2 I need through the stones. My 29 is going through a ladder and of course isn't turned up as high and is still around 950 or so. My 90 is around 700.


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## Rex Grigg (Jan 22, 2004)

I have two cylinders going right now. A 5 lb on a 20 gallon tank that has been going over a year. And a 20 lb feeding both a 55 gallon and a 29 gallon. It's been going over a year.

Common problems.

Used old washer when attaching regulator to cylinder.
Regulator not tight enough.
A leak in the system somewhere.
Use of the wrong tubing. Silicone tubing can lose up to 6% of the CO2 per foot.

And in your case an inefficient diffusion method may cause higher than normal CO2 usage.


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## steel1212 (Feb 21, 2006)

New washer
as tight as I'll get it before I think it'll crack
Tried spraying soapy water, no bubbles
I have regular airline tubing so that could be part of it.
I also have the airstones putting out a lot of bubbles do to the fact that it isn't diffusing as well as a good reactor.


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## TetraFreak (Mar 15, 2006)

Perhaps it's time to use those glass diffusors or a DIY Inline reactor...along with changing the tubing.


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## JanS (Apr 14, 2004)

Really 6 -7 months isn't out of the question for a 75 gallon tank. Part of it depends on your water and how much you inject too. With my higher KH, I have to keep it going at a pretty good rate to keep my levels where I want them, so I don't expect it to last as long as others do.

If you add a better diffuser or reactor and better tubing, that should help quite a bit too.


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## John N. (Dec 11, 2005)

My 10lb tank is going strong at 6+ months on a 29 gallon at about 1-2 bps. I suspect it will a last to a complete 8-9 months before I need to refill it. 

-John N.


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## kwc1974 (Jan 4, 2006)

My 5# bottle on a 55gallon tank will last 1.5 - 2months
my water is very hard(currently 16kh, in winter as much as 22kh), so I have to inject a lot to keep the level I need for plants.
I am looking for a solution that will work for me to lowering the kh.


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## jrIL (Apr 23, 2005)

On my 55 with very hard water I also have to use alot of C02. I get about a month out of a 5LB. bottle.

JR


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## akos (Dec 14, 2005)

Hey jrIL,

I understand that having a high KH does have an affect on the CO2 saturation, but you also show that you are injecting ~60bbM. At 1 bubble / sec, I think your 5LB tank should last a heck of a lot longer than a month. On my 46 tank, I normally do ~2bbs and get 6months running 24/7 out of a 5lb tank. That is with silicone tubing, so I know I have some loss there. I guess bubble counts can vary from counter to counter, so it isn't an exact science, but it seems to me that a 5lb tank should last longer than 1-2 months.


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## chrisl (May 24, 2004)

agreed, 9-10mos of 10# tank on 75gal running pH of 6.6


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## Rex Grigg (Jan 22, 2004)

If your 5 lb tank is only lasting 1-2 months on a 55 gallon tank then you have a leak somewhere. Or a poor diffusion method or a combo of the two. No matter how hard the water is you are just injecting enough CO2 to get to 20-30 ppm. and no matter the water hardness that's going to be the same amount of CO2.


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## kwc1974 (Jan 4, 2006)

> Rex Grigg wrote
> If your 5 lb tank is only lasting 1-2 months on a 55 gallon tank then you have a leak somewhere. Or a poor diffusion method or a combo of the two. No matter how hard the water is you are just injecting enough CO2 to get to 20-30 ppm. and no matter the water hardness that's going to be the same amount of CO2.


Rex, no leaks, that I can assure you of. Diffusion is with a stintered glass diffuser. It gets the co2 bubbles into a fine mist as can be expected, but the mist bubbles do not dissolve into the water as they should due to the hardness.
With a 2-3bbs I might achieve 6-10ppm, but to achieve 20-30ppm the bubbles come out too fast to count. I know that a external reactor would probably do a better job at injecting co2, but how much better.

I was under the impression that people with hard water just dealt with this fact. If there is a better way for me to achieve my co2 level without emptying my tank every month and still having a high kh please let me know. I have started to think of getting a RO unit but really do not want to hassle with it, I would like to keep this as simple as possible.


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## Rex Grigg (Jan 22, 2004)

I would try building an external reactor. Plumb it into the output of your canister filter and see if that doesn't work better for you. 

I have a series of pictures on my website that shows how to build a basic external reactor out of PVC.


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## Dave_S (May 11, 2006)

I was curies after going through a 5 pond cylinder a little quicker than expected. So I weighed the tank empty – about 7 pounds. After a refill at the local welding supply it was about 9. I asked if a 5# cylinder was supposed to hold 5 pounds of co2 and didn’t get a straight answer. So next time I needed co2 I went to a home brew store (one mentioned on this site - thank you) and exchanged for the exact same cylinder. Weighed it -12 pounds. Service was a lot better to. Don’t think the welding store is being dishonest, I think it was just sloppy work – takes 45seconds longer to properly fill the tank.


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