When your CO2 tank nears empty ....

[Delphinus]

... What do you notice first, do you notice the inlet pressure start to drop, or do you notice the bubble rate start to slow down every so often?

[pocilipora]

You notice the preasure guage preasure drop. Once the guage starts going down, there isnt much gas left anyways. You wont get very many days out of your tank once the preasure starts to drop.

[Jason McK]

How long (I know it will be different for every system) does the 10lbs tanks usually last?

J

[Delphinus]

Hmm, re-reading my question, I missed a little detail. It should read, "do you first notice your guage readings drop, or do you first notice the bubble rate slow ?" Sorry about that.

My cylinder is a 20lb. Filled it about 13 months ago. The bubble rate slows at night (only at night). So every morning I open my needle valve a wee tiny bit to compensate. Then it's fine all day, check it again at night, still fine, but by morning it will have slowed again so I open the needle valve a little tiny bit more, and so on. It can slow as much as half, which to me seems a significant rate change.

Going on like this for almost two weeks now.

But the inlet pressure hasn't budged. Still reads 800psi, same as it's ever been since it was filled. Maybe the guage is stuck.

My needle valve is incredibly fussy. Like, if you so much as touch the valve, it will change the bubble rate even though the valve position does not change. Is this normal, are they all like this? Or is this goofy. I run my outlet pressure at about 20psi.

[pocilipora]

It depends on how much demand for calcium and cabonates your tank has. The more Co2 you use, the more you can get from your reactor. I had a 10lb tank last over a year and a half. But that didnt last once my corals started growing.

[trilinearmipmap]

As far as I understand, when your CO2 tank is approaching empty the bubble rate should increase. Something to do with the way the regulator works, anyway can someone let me know if this is right?

[Andy]

When my CO2 tank is nearly empty, I notice an increase in the bubble rate. Happens every time.

[Delphinus]

An increase. Hmmm. Someone is filling my cylinder with more CO2 then in the middle of the night ??? Gremlins!

No other theories on a mysterious bubble rate slowdown? Happens only at night ... happens every night ... and every day the needle valve opens a tiny wee bit more to compensate. Sooner or later I'm going to get to the end of the needle valve .......

[EmilyB]

I dunno....kari said the needle will drop suddenly and then you go for a refill.....

[Aquattro]

Tony, I would double check for any leaks in the system.