Fluctuating CO2 Output

Rob Steer

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23 Feb 2008
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Hi,

I'm currently using a Dennerle 500g refillable cylinder and classic regulator for about a month now with no problems what so ever. However yesterday morning I noticed that the fish were gasping at the surface! Upon checking my drop checker the CO2 levels were off the scale (120ppm) :wideyed: , when I checked the C02 equipment I noticed that the first gauge was reading ~25 bar (normally 50 bar) and the second gauge read 1.7 bar (normally 1 bar) :? I reset the gauges back to their normal operating pressures, but awoke this morning to similar readings (fish are fine though as I increased surface agitation). Have I got a faulty regulator or does the operating pressure increase as the contents of the cylinder decrease, it doesn't seem logical to me?

Rob
 

ceg4048

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Hi,
The contents of a CO2 cylinder is actually liquid. As the contents decrease there is more room for the expansion of the liquid and this creates a surge. This tells you it's about time to refill the cylinder. 120ppm CO2 sounds almost impossible and would almost certainly wipe out the population in short order. How are you measuring it?

Cheers,
 

Rob Steer

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Derbyshire
Hi Ceg,

Via a Dennerle drop checker, the colour is referenced to the indicator strip which comes with the kit:

Blue ~5ppm
Dark Green ~20ppm
Light Green ~40ppm
Yellow/Green ~80ppm
Yellow - 120ppm

Normally the indicator is green which I guess is roughly 30ppm.

Rob
 

ceg4048

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Hi, that would be true if the water in the drop checker is not tank water. Is it 4dkH distilled water in the checker? If not you might consider getting some from AE.

Cheers,
 

Rob Steer

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It's definitely not tank water, it's the refill solution supplied by Dennerle, it comes in small pouches and the liquid is blue.

Rob
 

ceg4048

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Hi,
Interesting. It must be a pre-mixed distilled water solution with a few drops of bromo-blue and with kH adjusted to somewhere between 4 and 6 perhaps. I didn't realize Dennerle were supplying this now. In any case you may wish to consider using a bigger cylinder like a Fire Extinguisher. Monthly refills could become annoying unless you have several cylinders in reserve. There is a FE how-to sticky in the CO2 section.

Cheers,
 

Rob Steer

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Funny you should mention that.... I have an FE coming this week. If I run out of CO2 what is the drill? I don't really want to go and refill knowing my FE is due to arrive this week.
 
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Occasionally you can find a seller on ebay that does 2kg CO2 bottle for 30 quid including delivery. It's not one of the FE bottle. It's one of the bottle with a nice grey colour to the body and a very sturdy look with nice red knob on the top to twist to open. Keep an eye on ebay and if you come accross that item, buy it as a spare. I've got 2 bottle spare and a 10L bottle CO2 running atm. lol
 

ceg4048

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Rob Steer said:
Funny you should mention that.... I have an FE coming this week. If I run out of CO2 what is the drill? I don't really want to go and refill knowing my FE is due to arrive this week.
My drill is to turn the lights off until the replacement comes and to pretend I'm doing a blackout. There is a direct link between light and CO2 demand. Not having sufficient CO2 when demanded can cause all sorts of algae issues. The plants will be OK if it's only a couple days wait. It's probably a good idea to refill the 500g though, and to have it on standby for future backup.

Cheers,
 

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