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Discussion Starter · #1 ·
I'm feeding CO2 to two tanks, a 20 gallon and a 40 gallon (60 gallon filled 2/3). It's a 5lb cylinder and I'm using a inline atomizer on the 20 gallon and an in-tank diffuser in the 40 gallon. Both have drop checkers and are typically a light green color (lighter than lime green but fish are tolerating it). Let's say I have 30ppm to 40 ppm in each tank and run it 8 hours a day. Would this deplete a 5 lb cylinder in 6 weeks?

I have a bubble counter on the 20 gal but not the 40 (just ordered one). I run about 7 or 8 bps on the 20. Feed pressure is at 40 psi.

I also just realized the CO2 has been running constantly for the past 80 hours (shuffled some things around and forgot to reconnect the timer), so that ate up 10 days worth of gas. Even then, 6 weeks seems awfully premature.
 

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I get 2.5 - 3 months out of mine running about 2 bps 8 hours daily in my 55 gallon.
At the 7-8 bps you are pumping into your tanks, 6 weeks sounds about right based on my experience.
 

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I get 2.5 - 3 months out of mine running about 2 bps 8 hours daily in my 55 gallon.
At the 7-8 bps you are pumping into your tanks, 6 weeks sounds about right based on my experience.
check leak, 2-3 month is too short on a 55 gallon tank, with 2bps.
 

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Never considered that possibility as I was content to replace it every 3 months. Would have to be a pretty slow leak to go that long. But thanks for pointing out the possibility...I'll check it next time Im messing around under the tank as it would be great to get a few more months out of it.
 

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Hi @mossman77,

I have a 75 gallon that only allows me to fit a 5# CO2 cylinder under it in the cabinet. I track my CO2 filling and typically it is 3 months between filling. I don't use a solenoid on the systems so the CO2 runs 24/7. I also don't run high CO2, typically 20 - 30 ppm. -Roy
 

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At 1 bps you will use about 6.5 - 7 grams of CO2 every 8 hours.(Assuming the bubble is approximately a sphere of 3mm radius and using the molar volume and some math I have not applied in 20 years....) Using up all the CO2 in 6 weeks seems about right.

wt of CO2 in grams @1bps for 8 hours =

Volume of Bubble(in liters) X 3600(per hour) X 8(hours/ day)
---------------------------------------------------------------------X 44(molar weight of CO2)
22.4(liters)

This is just an approximate value. take it with a pinch of salt. :)
 

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Discussion Starter · #8 ·
I should have weighed the bottle to make sure it was full. It had been sitting out in direct sun in 90+ degree heat when I picked it up. I picked up two more bottles today and found that one only has 3.5 lbs in it and the other 4.5 lbs 😕
 
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