Viable CO2 Injection System?

[amhodge]

I'm planning to put together a standard 2L bottle CO2 system and have been considering what to use as a diffusor. At the same time I've just picked up an air pump from a thrift store and have that running into an airstone buried in my gravel.

Here's my idea: in order to run fewer airlines into my tank I'm thinking about running a line from my air pump into the CO2 bottle, then a second line from the bottle to the airstone.

Is this likely to be effective? Is it likely to explode? Has anybody heard of a similar setup, or can anybody point out potential problems with it?

Thanks!

[nickmcmechan]

Sounds fine to me.

I used a 2l bottle, but wasn't happy with it so switched to 2 x 1l bottles. I'm now on 3 x 1l and I refresh the mix on different days.

[nickmcmechan]

And should have said this keeps my CO2 at 10-12ppm in a 30G.

[amhodge]

Thanks, Nick. I keep a 30gal as well. What's the difference with the 1l bottles?

[Ketso]

I see one major potential problem. You are running your Co2 into an airstone which is almost as ineffective as not having Co2 at all. You need a way to keep it in contact with the water until it is fully diffused into the water.

Currently, your bubbles are in contact with the water for as long as it takes for them to leave the airstone and pop on the surface. If you want to run Co2, you should do away with the air pump altogether. It will only agitate the surface allowing your Co2 to "gas off".

As for the Co2, you need a diffuser. A bell or power diffuser or etc. to make the best use of the gas in your tank.

[amhodge]

Thanks, Ketso. I'm interested in hearing more opinions. I wish I knew what site I was on earlier so I could reference the article (might have been the krib), but I read that running a bottle CO2 airline to an airstone was an effective diffusor.

This "gassing off" problem is a concern. I'm not in love with the aesthetics of the airstone but my fish are in love with the current. Would putting distance between the diffusor and the airstone help?

[amhodge]

Here it is: http://www.tropicalfishcentre.co.uk/Diyco2.htm

"To disperse the bubbles, you can do any of the following...: place an airstone on the end of the tubing and anchor in the aquarium..."

[Ketso]

After a bit of reading, I will partially retract my statements above. It would seem that some say an airstone will work (contradicts everything I have been told here and on other forums).

However, I really dont think the addition of an air pump will aid with the Co2 diffusion. An airstone's effectiveness would have to be somewhat limited, IMO. The air bubbles would almost certainly cause too much gas off.

If you decied to go this route, I'm interested in the results.

EDIT: after looking at that link, right below the line you quoted, it says "Airstones and diffusion bells are less efficient than reactors and filter dispersal." Which means it WILL work. It just wont work great.

[Madcrawdad]

running an air pump period will increase your off-gassing of CO2....I would think that running your air and CO2 thru the same line would increase off-gassing of CO2 even more. IMO I wouldn't run any pumps, especially w/ DIY CO2.

[amhodge]

What you both said makes sense and at the very least I'm believing I ought to keep my airstone and CO2 diffusor separate though I'd still like to keep them in the same tank. I'll have to measure my CO2 when I get them both going at once.

Fortunately I dont have much in the way of plants yet as that part of my tank is in its planning stages.

[J double R]

I use a limewood airstone (commonly used with protein skimmers) on the end of my airline. the bubbles are easily compared to an expensive co2 diffusor, are cheap and easily replaceable once clogged, and coupled with the placement near my canister filter's output, results in the tiny bubbles staying underwater for an extended period of time, bringing nearly 100% diffusion.

running an air pump through the bottle, may likely upset the anaerobic life cycle of the yeast, which doesn't need any oxygen to create the byproducts of co2 and alcohol. I'm not sure what the result would be, but I don't believe you would yield the same results (or if you did, it would be excessive and inefficient) as if you used the co2 from a sealed system.

[nickmcmechan]

Thanks, Nick. I keep a 30gal as well. What's the difference with the 1l bottles?
Sorry, should have explained the reasoning behind the multiple bottle.

When I had a 2 litre bottle my CO2, kH and pH levels rose and fell as the CO2 levels rose and fell from one bottle, as the yeast activity rose and fell and eventually died off.

I didn't want this, I wanted a more stable environment for my inhabitants...fish, plants and all.

So what I run now is 3 x 1 litre bottles. I change the mix on different days so that the peak of CO2 from one bottle coincides with the trough of CO2 from the other. This way I maintain more consistent levels of CO2 from my DIY setup.

I was running the CO2 in from my internal filter. I have removed that to another tank which is not CO2 injected now, so I now run it from an airstone.

A dedicated CO2 airstone is OK, but I would combine it with air. I put my airsone at the other end of the tank from my ugf output where I have a still spot of surface water. Its tucked under a load of plants so that when the bubbles hit the leaves they will disperse. This is also near the output of my cannister filter spray bar, to help duisperse the CO2 throughout.

However, I do plan to switch to a CO2 ladder for better dispersal.

The output of my ugf is not straight up and has a 'head' on it which points horizotally. I point this to the rear of the tank to minimise surface agitation, which works OK. So, I still get the benefits of my ugf which I like.

So, in summary I setup the CO2 output in the quietest part of the tank. I use 3 x 1 litre bottles. I change the bottles once per week each, one on a Tuesday, one on a Thursday and one on a Sunday. Thsi lines up with my pwc schedule. I plan to change the arstone to a glass diffuser.

I would appreciate opinions on my methods, but is does get me 10ppm + CO2, which is good enough for me combined with bright lighting, a reflector, root tabs and liquid ferts...

[amhodge]

Lots to consider!
JR, thank you for the basic lesson in life sciences. I think you're absolutely right.
I'm going to steal some ideas from you, Nick. I'm thinking of putting my airpump line under a gravel-to-surface pile of wood. I expect this will limit surface agitation as the bubbles take longer routes and disperse in smaller increments (and improve the look), then I can set my CO2 at the other end of the tank, in a still spot as you said under some plants, or under my filter as JR suggests. Though instead of tucking the airstone under plants to disperse the CO2, would it not be as effective to bury it in the gravel?

[nickmcmechan]

I've not tried the under gravel thing yet, so interested to hear opinions on this anyone?