# Co2 Diffuser



## jgalbraith (Oct 27, 2012)

Hi there,

We just set up a new Co2 system in our tanks using glass diffusers. It's working fine, however the bubbles coming out of the diffuser are beading together and are too big to be absorbed into the water. Does it take a while for them to work properly? Or do I need to do something to adjust it?

Thanks for your help.

Joanne


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## Darkblade48 (Jan 28, 2008)

It is possible that the glass diffuser's ceramic disc is just not that good. Some discs have finer pores than others.

If your disc is dirty, or you suspect it is dirty, you can place into bleach for 10-15 minutes, and then rinse in water before placing into a solution containing 2x the recommended dechlorinator to remove any remaining bleach.


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## aniroc (Aug 23, 2012)

I have a yeast and sugar CO2 bottle with an airstone that I replaced with Fluval ceramic disc because of some growth I got on the stone. And I also noticed some very big bubbles but also a fine "mist" coming out of the diffuser. However, the pressure inside the bottle is much higher now, I'm affraid it might explode (I wrapped a towel around the bottle, just in case..)


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## Darkblade48 (Jan 28, 2008)

aniroc said:


> I have a yeast and sugar CO2 bottle with an airstone that I replaced with Fluval ceramic disc because of some growth I got on the stone. And I also noticed some very big bubbles but also a fine "mist" coming out of the diffuser. However, the pressure inside the bottle is much higher now, I'm affraid it might explode (I wrapped a towel around the bottle, just in case..)


I would personally not recommend using a ceramic disc diffuser with DIY CO2 for fear of the bottle exploding and spraying the room with the yeast/sugar mixture.

It is not a common, but not an uncommon accident.


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## aniroc (Aug 23, 2012)

Should I go back to the airstone? Can I make it safer by adding another empty bottle along the line? I thought that the big bubbles are because of the high pressure.
The airstone worked pretty good except for some fungus/bacteria slimy growth I got on its surface. And the bubbles are not that fine like with the diffuser. I wrapped the bottle in a towel and put everything in a plastic bag. I am keeping my fingers crossed...


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## Darkblade48 (Jan 28, 2008)

aniroc said:


> Should I go back to the airstone? Can I make it safer by adding another empty bottle along the line? I thought that the big bubbles are because of the high pressure.
> The airstone worked pretty good except for some fungus/bacteria slimy growth I got on its surface. And the bubbles are not that fine like with the diffuser. I wrapped the bottle in a towel and put everything in a plastic bag. I am keeping my fingers crossed...


It's up to you. Plastic bottle explosions can happen, but I don't want to spread unnecessary fear either. It is like saying car accidents happen, but I don't want to scare you to the point you refuse to get into a vehicle.

Adding another bottle along the line won't mitigate the risk of bottle explosion, if it occurs, but it can help prevent the fungus/slime that grows on the airstone (it may eventually grow on your diffuser too). The problem is once the slime clogs the airstone/diffuser, there is no way for the CO2 pressure to escape.

To minimize the risk of the bottle exploding, just make sure you keep your diffuser clean and clog free. If you are really paranoid, you can put the entire 2L bottle into a plastic bucket and cover the top with a towel (I think exploding shards of plastic would have no problem penetrating plastic bags).


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## aniroc (Aug 23, 2012)

How much pressure could build inside?
I unscrewed the lid and it made the same sound like when you open a Cola. 
I will get a longer airline so the bottle will sit in a bucket, under the tank, with towel all around.
Do you know what the slimy thing is?
I really want to get into the pressurized CO2 when I'll gather enough knowledge.


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## Darkblade48 (Jan 28, 2008)

aniroc said:


> How much pressure could build inside?
> I unscrewed the lid and it made the same sound like when you open a Cola.
> I will get a longer airline so the bottle will sit in a bucket, under the tank, with towel all around.
> Do you know what the slimy thing is?
> I really want to get into the pressurized CO2 when I'll gather enough knowledge.


I don't think the pressure has ever been measured, but some ceramic disc diffusers require 30 PSI to build up. I am not sure what pressure the pop bottles are designed to hold back.

It is probably fine; the scenario I described is a worst case one.

I am not sure exactly what the slime is (some people speculate it is yeast, bacteria, etc), but it occurs with DIY CO2. A gas separator seems to slow down its formation.

For more information regarding pressurized CO2, be sure to take a look at my pressurized CO2 guide below. It is good timing as well, since I will have a few more CO2 regulator builds available soon.


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## Newobsession (Nov 17, 2010)

If you want a decent defuser that falls between the Fluval ceramic and an airstone, you can p/u a wood diffuser. I think BA's refers to them as lime wood, or at least used to. I used them before I went pressurized. AS as Darkblade mentioned, the white slime/growth is standard for diy CO2. I solved the problemwhen I built a diy bubble counter as if I am not mistaken it works on the same pricipal as the gas seperator.


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## pat3612 (Jan 29, 2008)

A ladder diffuser is a good choice too, I always found them very effective, never had any problems and they are easy to clean you can get them at BALs.


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## LTPGuy (Aug 8, 2012)

*Max pressure in pop bottle.*

I've done some googling not too long ago and read that the 2L pop bottle can withstand up to 100psi.

I have personally and repeatedly filled a 2L pop bottle with CO2 to 60psi.

I can't comment on other things, but have noticed that "CO2" out of a yeast setup is not the cleanest. There are always build up and smell.


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## hoody123 (Oct 24, 2012)

I can update and say we (OP is my wife  ) simply needed to be a bit patient (not the strong suit of either of us), the diffusers started working exactly as expected within about 48 hours.


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## Fishfur (Mar 4, 2012)

Fwiw, if you look up DIY C02, some methods call for one bottle, with the C02 tube going from the cap to the tank. Others call for two bottles, using a second one that can be smaller in size, between the yeast bottle and the tank. They are linked with tubing, and the gas goes from the first bottle that contains the yeast mixture, into the second bottle, which is partly filled only with water, and then from that bottle into the tank. So the second bottle has two tubes in the cap, instead of one.

I would not, btw, use a water bottle for this. I don't think they are made to withstand the same kind of pressure than soda bottles are made to withstand. As was posted by LTPGuy, they can take a lot of pressure, far more than is likely to be generated by a yeast bottle unless it has no outlet at all for the gas. So keep whatever you do use for diffusion clean. Whether it's an airstone or ceramic diffuser, you need to prevent it from clogging up.

This two bottle system is supposed to, [and I have not used it myself yet, so I'm only going on what I've read] but it is supposed to help cut down on that slimy gunk you get building up on airstones, etc. The slime does come from the yeast bottle and is likely bacterial, though it does not appear to be toxic in any way to tank life. I've never seen a report of it causing toxicity problems. But by passing the gas through the second bottle, you may be able to reduce the amount that builds up, maybe by quite a bit.

One thing I have tried is using mini 'bulkhead' fittings to get the tubing into the bottle caps. Because pop bottles are made to withstand some serious pressure, I'm not too worried that one will explode. But I must admit, that if there's a defect, explosions are possible. Anything under pressure has at least some potential to explode. Even so, you need some amount of pressure to make diffusing devices function well. And I also suspect quite a few problems that happen with DIY bottles, in terms of lack of pressure, may well be due to a less than perfect seal around the tubing as it leaves the bottle cap. If you drill the hole a bit too large or it's a bit irregular, even if you slather on silicone to seal it, it may not give you a really tight seal. The bulkheads certainly do that.

The bulkhead fittings, incidentally, are normally used for hooking up fuel lines in Remote Control airplane engines. RC hobbyists use the same size silicone tubing for fuel lines as we do for airlines, so they fit our tubing too.

Because the bulkheads make for a very secure seal, they can help increase the pressure buildup, which should make an airstone or diffuser work better. It will still require a bit of time to build up enough pressure in a new bottle, but once you do, should be good until the alcohol percentage in the bottle gets high enough to kill the yeast. By then you should have started a new bottle anyway. And so long as the C02 can escape the bottle, an explosion is not very likely to happen. But I think putting the bottle in a bucket is a fine idea anyway, after all, better safe than sorry. Accidents DO happen.

Btw, the bulkheads are made by a company called Four or Fore - Most. Sorry, I'm not sure of the spelling. I got them from a local hobby store, who were kind enough to order them for me. You get two in a pack, one green and one red, for about six bucks, I think, with tax. A bit of a challenge to get the tubing attached to them, but not too bad.


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## SignGuy (Mar 3, 2012)

+1 to what Fishfur said on the bulkhead fittings. I currently use them on my Diy setup and they work very well. i found out that they actually come in two sizes though.

Most of the info you see online show the red/green combo but Fourmost also make a blue/yellow set that are about 1/16" bigger I believe. It's not much, but the tubing fits just a little bit better










Definitely helps to have that second bottle inline as well. I use a smaller 500ml (or so) pop bottle. Doubles as a bubble counter too.


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## CanadaMoe (Sep 12, 2012)

*It CAN happen!!!!!*

Hello Everyone,

Sorry, didn't want to hijack this post, just want to share an experience I had with a CO2 DIY some years a go.
I have kept the bottle as a reminder to myself to be careful.

The bottle exploded beside the tank and it was a mess!!! It was very fortunate that it happened when no one was around. The aquarium was beside my desk. There was glass found about 15' away. The reason the cap is on was I had an algae problem in the tank that this bottle was connected to. So, I removed the nutrient source (CO2) and instead of throwing the whole content away I thought I'd keep it until the algae problem was under control. I do recall that it was unusually warm in the office at the time and I think that might have contributed to making the yeast over zealous.


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## aniroc (Aug 23, 2012)

Wow!

But why does it have a cap?

Now, about the second pop bottle along the line....How much water should I fill it in? Because, air (or CO2 gas) is more compressible than a liquid and I would leave more air in that second bottle. An airline from the yeast bottle to bubble (no airstone needed) under the water lever in the second bottle and from there (just below the cap) into the diffuser in the tank. And of course, a check valve somewhere. In this case, do I equalize the pressure between the two bottles?


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## SignGuy (Mar 3, 2012)

Technically I don't think you need any water in that smaller bottle as it will ultimately fill completely with gas. I believe the waters is really just there so you can actually see the bubbles.

I have mine about 1/3 full with water - approx 150-200ml. There is a piece of rigid airline coming down form the input fitting to just below that water line. The outlet hole that goes to the tank just has the bulkhead fitting - no tubing inside the small bottle.

As for overall pressure, i would say that it's no more than a typical bottle full of pop.

if you have not already read this, http://www.qsl.net/w2wdx/aquaria/diyco2.html, it's a great starting point.


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## GAT (Oct 8, 2011)

You can keep the CO2 tube under the filter intake to maximize the absorption. 

Don't make this complicated, I followed a simple method suggested by Solarz and its working pretty good. Just one soda bottle and some airline tubing, I've been using for close to 5 months without any issue.


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## Fishfur (Mar 4, 2012)

The water in the second bottle, I believe, serves as a sort of filter for the 'gunk' that tends to build up on the diffusing devices. I could be wrong.. it would certainly not be the first time, but I think that's the main reason it's there.

And as I said, if there's a yeast bottle with no way for the gas to escape.. an explosion is definitely possible. Yeast will continue to grow, and produce C02 for so long as it has food or until the alcohol percentage gets high enough to kill it. So a sealed container with live yeast in it that's growing is going to keep right on making gas. We live and if we are paying attention, we learn .

Wish I'd known about the bigger fittings.. would have been easier to set up. Oh well..


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