CO2 diffusion tubes

[Vjarn]

havent done it yet but heres the plan and was hoping for input.

CO2 soda stream bottle

release valve

pipe

glass or plastic tube

the way it works is that it'l be all connected air tight and the glass tube would be attatched to the back of the tank upside down to hold air in (CO2) and the CO2 would diffuse out of the tube at a steady rate. to refill the tube just let some more gas out every now and then.

what you's think??

[Lucid]

It would work, as most of the diffusers are bell shaped, which gives a larger surface contact and what I beleive a more steady and even distrubution. I would look into attaching a bubble counter and then you can set it to disperse at your own set rate and it also means you don't have to remember to fill the tube all the time as it will slowely drip feed in and fill as it disperses.

B

[suphew]

I think you would find that manually having to add CO2 would become a pain, plus what happens when your on holiday or even at work, I would go with Ballistic's suggestion and add a bubble counter there are plans for DIY counters on reefcentral.com, they are really simple. I just made one for myself using a hospital drip and filling the drip counter part with water, and bending the tubing on the CO2 feed up past the main drip part so the water doesn't drain back when it runs out of gas.

As far as the diffuser I would be looking at something that was more actively mixing the CO2 and water, with the contact area being so small I'd be surprised if it helped much. Most commercial diffusers force the CO2 bubble to follow a long path in water to get them to mix. I have to DIY suggestions, I have used both to good affect

1) used a piece of 1inch tube (from an UFG uplift) about 4-5 inches long, feed the tube from the CO2 down the middle then wrapped it round the outside in a sprial going back up. I connected the CO2 tube to the larger using cable ties. The clever part is to put a small hole near the point where the CO2 tube reaches the bottom and starts to sprial back up. This hole allows the CO2 to draw water in as it goes past. With mine I could see the bubble of CO2 shrink as it traveled up the tube and diffused in the water, there was no bubble by the time it reached the end. NB: doing it this way also saves you making a bubble counter because you can see the bubble going up the tube.

2) The best diffuser I setup was to put a hole in the start of the return hose from my external filter (I actually put the hole in the rubber part that holds the hose in place so it had a good seal) In the hole I pushed a plastic air line joiner thing and connected the CO2 to this, by the time the CO2 had worked its way up the hose and into the tank it was well mixed.

As an aside do you have any air bubble things running in the tank? If so you might want to think about taking them out, the surface turbulance and air movement will drive the CO2 out of your water.

[Luke*]

I used an upside down 300ml coke bottle for a while that worked well weighted down with sinkers and hidden in the plants. If you've got something long you might wanna put some mesh over the end so fish don't get inside and get trapped.

[HummingBird]

They'd just fall back down into the water if they got inside wouldn't they...

[Vjarn]

nah they couldn't get up cause it'll be full of CO2, i might try something else like a spiral so the bubble can spiral upwards in a long slow journey to the top. thanks for the idea. still going to use a sodastream bottle, get a second hand one and it only cost $5 to fill. i bet that'll last a month.

[Luke*]

Just make sure though if the CO2 runs out that it doesn't create a water pocket that the fish could get into and get trapped. It's an old fishing method used in a similar way where the fish go in to the get the bait and can't find their way out.

[Dark]

was talking to a chemical engineer regarding the diffusion of CO2 - his response was;

'CO2 is heavier than air, so if it escapes to the surface of the water it will just displace the air above the water and then the entire top of your tank becomes a [bell]'

thats a nice big bell!

apparently unless you are putting the bell about 10 feet underwater you will not make a noticable difference to the diffusion rate.

useful to note if you have fish (eg gourami) that need to breathe air; if you are worried about the layer of CO2 on top of the tank being bad for them you'll have to watch that your bell doesn't overflow

complete diffusion is your best bet

[HummingBird]

You could try something that plantman on the forums here does, have the bubbles go into a powerhead where they get spewn out as smaller, easily diffusing bubbles.

[Vjarn]

ok just got an old soda stream maker and ripped it apart. so i got the top part the screws the bottle and the button that pushes the valve open, connected it to a hose and it goes into a wave maker that disperses bubbles of co2. its was a bit of a mission to figure out how to slowly push the valve open but i took out the small rod that pushes down on the valve and replaced it with a screw so you screw it down and it pushes the valve open. trying to get the right about on bubbles . got it at1 bubble every two seconds. $9 a bottle so see how long it llasts. i'll get some pics up soon.

took a pH reading and it went from 7 - 5.5 in onne day. so trying to slow down the bubbles but its hard.

[Dark]

you could try attaching a flow control to the line itself - a brass needle valve similar to the 'gang valves' you get for air lines?

look forward to the pics - considering that new soda stream systems can be got for less than $80 these days it sounds like a good deal!

[madcookie]

Hi all,

Have been reading thru all the threads on this site, and a few on other sites....still havent REALLY found an answer tho - so wondering if some of you DIY gurus might be able to help?

Am using several coke bottle setups on several tanks, all using eheim 2213 or fluval 04 series cannister filters. I read the link below, and found that sucking the co2 into the cannister filter might actually be dangerous - cause an "air"pocket in the cannister, up high where the impellor assy is, and cause it to burn out etc.

http://www.tropicalresources.net/phpBB2 ... 83075a8f24

Has anyone else heard of this happening?

Or....Is anyone else putting co2 into a cannister filter, and not having any problems?

Any thought, tips, and advice greatly appreciated!

[suphew]

I have done similar, but feed the CO2 into the start of the water OUTlet hose. This worked really well, but you need to have a one way valve so that when your bottle runs out it doesn't fill with water.