# How long would a 500g or a 2kg cylinder last?



## Swan900

I roughly want to run it at about 2bps max. My regulator is fitted with a good solenoid and I was just wondering how long at that bubble rate would a 500g cylinder last as well as a 2kg cylinder? Thanks ahead of time!

Swan


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## Themuleous

How big is the aqurium? Thats more of a factor  Why do you say 2BPS max?

Sam


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## Dolly Sprint 16v

Themuleous said:
			
		

> Why do you say 2BPS max? Sam




Well got to put a peg in the ground somewhere or set a bench mark.

500g @ 2bps should last about 8 - 9  months 
2kg - live time.

Stick to 2 kg or bigger bottles or FE's as once you get going with your tank the injection rate will be higher than 2 bps -I started at 2 bps, now I am pumping in that quick cannot count the bubbles - 2kg last me 8 - 10 weeks.

Regards
Paul.


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## Swan900

My tank is only a 60L moderately planted. 3bps will be about max rate I will have it. Cheers Flyfisherman for the great help. Would be a perfect amount for me the 500g as the size is also a benifit! Thanks mate!

Swan


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## Themuleous

Just wondered that was all  the bubble rate for a given tank depends on loads of factors.  2bps might not be enough that was my only thought.

Is it a high light tank?

Sam


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## JamesM

Swan900 said:
			
		

> My tank is only a 60L moderately planted. 3bps will be about max rate I will have it. Cheers Flyfisherman for the great help. Would be a perfect amount for me the 500g as the size is also a benifit! Thanks mate!
> 
> Swan


I've run at least 6bps on a 60 litre before. Use a drop checker to measure co2, never trust BPS as it can vary from bottle to bottle.


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## Swan900

How long would a 500g last at 6bps then? As for my tank its moderately planted and has two 15W T8's. So 17 gallons would be roughly 2wpg. So is that high or medium? I had 2bps on my old system but it was a nano and had to rid of it as it was costing me too much to replace. So 2 maybe 3bps max was fine in my situation. And yes I do use a drop checker. But let's just see how 6bps goes. How long would a 500g jbl last at 6bps? Thanks again!

Swan


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## Charlieh

You can calculate the length of time your CO2 should last (in days) using this equation. I can explain the maths if you want but basically 1kg of liquid co2 will expand to form about 155 litres of gas at room temp and pressure and it follows from there but bubble size is very important. From my experience and what people report the equation seems to work well for normal pressurised cylinders but not fire extinguishers. My 3kg bottle lasts about 6-7 months at 3bps (JBL counter - estimate 6mm bubbles) for 7hrs per day

36141 * (weight of CO2 in kg) / (bubble count in b/s)*(useage in hours per day)*(bubble radius in mm cubed)

Use the weight of co2 in the cylinder not the total cylinder weight and a bubble size of 5mm diameter (2.5mm radius) is typical. Thus, for example 2kg CO2 @ 2b/s for 10 hrs/day will last for: 36141*2 / (2*10*2.5^3) = 231 days (7 - 8 months)


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## ghostsword

My CO2, 2kg JBL lasts about two months. Don't know about what amount of bubbles per second I have, I use the fish as a guide. If they are strugling on top, then I am dosing too much, and just tweak a little bit below that. 

I have a 100L tank, and although I am using high levels of CO2 I have never seen my plants pearl, but they grow fine.

What I know is that 2kg CO2 bottle works out much cheaper than 500grams.


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