# Newbie pressurized CO2 questions



## TheSmJ (Jan 22, 2005)

After using a yeast based DIY system for over a year to feed my 29G 2 WPG planted tank with CO2 and getting really, really sick of replacing the yeast every week or else ending up with a large BGA infestation, I finally decided to look into getting a pressurized CO2 system.

Here's what I'm buying:

-Milwaukee regulator/solenoid/bubble counter.
-5 or 10 LB CO2 tank (not positive on what size would be best quite yet).

I already have a Hagen ladder diffuser from my DIY system which I plan to carry over to my new system. Later on I may build a powered reactor, but for the time being this ought to do (I think).

Here is what I need to know:

About how long would a 5 lb tank last vs. a 10 lb tank last before needing a refill? 

About how many bubbles per minute would be appropriate for this tank, assuming the diffuser is as efficient as possible?

How many ppm of CO2 should I be looking to achieve? If memory serves 30 ppm would be best, but I'm not sure.

How EXACTLY does one test CO2 levels? I believe you need to check Kh and Ph levels, and measure the difference of these two levels both with and without the CO2 added. Is this correct or am I missing something?

Any help would really be appreciated.


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## hoppycalif (Apr 7, 2005)

I used a 5 pound CO2 tank for the 29 gallon aquarium I had, and it lasted about 6 months. Obviously a 10 pound tank would last twice as long.

It's hard to guess the bubble rate needed for a tank, since that depends on the size of the bubbles and how you get it into the tank, as well as what factors cause loss of CO2 from the water, such as surface movement and some filtration methods.

You can run about 30 ppm of CO2 in the water without bothering the fish too much, and that is enough for the plants even with high light intensity. You can measure that concentration using a drop checker as described in http://www.aquaticplantcentral.com/...aquarium-projects/32100-diy-drop-checker.html. No other method gives an answer accurate enough to mean anything, unless you spend over $1000 for a testing device.


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## bdement (Jun 4, 2007)

TheSmJ said:


> About how long would a 5 lb tank last vs. a 10 lb tank last before needing a refill?
> 
> About how many bubbles per minute would be appropriate for this tank, assuming the diffuser is as efficient as possible?
> 
> ...


The 10lb tank on my 46 gal tank has only needed to be refilled yearly. Depending on the size and use of your canister, you could get as few as 6 months or as many as 18.

Most people go by bubbles per second through the bubble counter. If you have fish in the tank, be cautious of CO2 poisoning and start LOW (.5 bps or something almost imperceptible), and work your way up over several days. I don't think the actual BPS pr PPM values are as important as keeping your fish alive as long as you're seeing good growth in your plants. You can compare your fishes respiration rates before and after to see if they're having trouble with too much CO2 in the water.

BTW the ladder diffuser is woefully inefficient, so without upgrading your diffusion method you won't be getting the most (or much, even!) out of your fancy new pressurized setup.

The PH vs KH scale is a good way to check CO2, or for continuous monitoring, you can get what's called a "CO2 drop checker."

Another thing to research when starting pressurized is the "end of tank dump," which can occur with some regulators when a CO2 canister gets too low.


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## TheSmJ (Jan 22, 2005)

I read all about the "end of tank dump" last night. I figure I'll just keep an eye on the tank and simply not allow it to get too empty. I also may get a release valve to dump the tank automatically and safely if the pressure gets too low.

I know the diffusion method I'm planning on using isn't the best by any means, but when placed in front of my cannister filter's spraybar it should do the trick. I thought about making a reactor inline with the output of the filter itself, but since it's a HOT Mag it would be difficult to pull off.


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## TWood (Dec 9, 2004)

With a needle valve in place the dreaded end of tank dump is mostly avoided. It's more like an end of tank wheeze. If you are running at the top end of CO2 saturation it will stress the fish, but if you are running CO2 at a mid-range, you and your fish will likely never even notice it.

If you have any inclination that you might get a bigger (or another) aquarium in the future then you really should consider getting a 20LB CO2 cylinder. Why? Because that is the default industry 'standard' size. Why? Because it's the largest size a single human can easily carry, and it fits under a standard countertop, which has made it the standard for every restaurant and bar that serves carbonated drinks. The 20LB cylinder is everywhere and in large quantities. Where I live, that means that a 5LB cylinder costs $12 for a refill (they only swap) and a 20LB costs $15. Do the math.

Also, do not buy a cylinder from anywhere except your local welding supply shop. If you take in your shiny new expensive 5LB aluminum cylinder and ask for a refill, you will get back a beat up old iron cylinder in trade.


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## TheSmJ (Jan 22, 2005)

I picked up a 5LB cylinder from my local welding supplier - lucky for me I have an Airgas store about 2 miles from my house and I hadn't even noticed until yesterday. 

I can "trade up" the tank if I want to go with a 20LB cylinder later down the line. As it is, 5LBs fits nicely in my tank cabinet and I have no problem spending $13 every 6 months or so for the convenience.


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