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NOTE: THE FOLLOWING WAS SPLIT FROM THIS TOPIC:

http://ausaqua.net/forum/index.php?showtopic=8610

Hi all,

I'm no expert on lighting but have anyone tried building their own CO2 reactor?

This is taking me back to my old High School days when funds were low but I was still an eager hobbyist. I have read somewhere (I can't remember where though) and have made and used a homemade CO2 reactor. Quite simply it uses the principle of fermentation. This is achieved by using good ol' bakers yeast and brown sugar.

All you need is an empty softdrink/juice bottle (1.5 to 2 litre bottle) with a screw top, air line, air valve/one-way valve (optional) and silicon glue to set this up. Then you'll also need bakers yeast, brown sugar and water which are your consumables.

The only major prep is to drill a hole on the bottle cap, then feed your air line through and put some silicon glue around the air line to prevent any leaks. I find it easier if you use a shorter length air line on the bottle cap, then place a connector or an air valve/one-way valve on it later.

Once the silicon glue is set and dry, simply fill the bottle 3/4 full and add 1 tablespoon of bakers yeast and 4-5 tablespoon of brown sugar. Replace the cap, give it a good swirl so the yeast settles and hey presto fermentation can begin.

the next step is to connect and air line to the aquarium and within a day or so, CO2 will be bubbling out (though at a slow rate) into the aquarium.

You will need to replace the water/yeast/sugar every week or a couple of weeks when the sugar is consumed and the water turns to alcohol. I should also advise that you should not attempt to drink this concoction as a little birdy once told me, it's pretty ranked :)

I have used this in a planted 2ft aquarium, but for a larger aquarium, it would probably need more reactors to give the plants sufficient CO2.

Also I have read (just today coincidentally) in an old issue of Tropical Fish Hobbyist Magazine (Feb 2007) that the best way to check CO2 levels in the water is to check the pH first thing in the morning (before the lighting comes on, before CO2 injection and the aquarium receives adequate aeration overnight). This is used as the standard. Then measure the pH 4-5 hours later (this is when the air valve comes in handy on the CO2 reactor - keep it turned off (but not completely as a fresh mixture of yeast and sugar can very quickly build a lot of pressure) the night before). If the pH level is higher (more basic) than the standard after 4-5 hours of CO2 injection, then CO2 injection is insufficient. If the pH level is slightly lower then CO2 injection is adequate. And if it is significantly lower, then the amount is excessive.

Of course this article refers to a proper CO2 injector. But no reason why it is limited to just that...

hope this gives you some food for thought.

p.s. awesome setup you have there Peter16 :wacko:

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I use DIY CO2. The recipe I use is 3/4 cup of sugar and 1 tsp pf yeast (and a pinch of bicarb)

You really shouldn't shut the DIY Co2 off at night, even if you just restrict the outlet, or the bottle is very likely to explode. Apparently you can add an airstone at night to gas off the Co2 - but I have enough to worry about in the fishroom already!

Also make sure your reactor is not higher than the tank or your scummy fermented stuff may siphon into the tank.

This should probably be in a separate thread. But I am having a holiday from modding the forum today. Any other mods who want to step in are most welcome.

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I don't really understand the science behind shutting off your CO2 at night. Plants can consume CO2 both with and without light, therefore there is no need to switch off overnight IMO. I guess it may 'save' some CO2, which would make sense with a fancy injection system I guess.

I had a DIY setup for years on my tank and it was great. It was a 2litre bottle, some airline and an airstone in the tank. We even used some lemon cordial that had gone off and it seemed to work great. If you want to be really safe you can add a check valve in the line to avoid possible back-siphoning when your bottle gets old.

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Plants actually absorb oxygen at night and CO2 during the day. As for your wpg target, a tank of your size (approx 220L/57gal) at 3wpg will need 180w, give or take. Above my 2ft (70L/18gal) I have 48w, for 2.7wpg... I can grow most anything under this light.

A note on the T8 globes. As these are your average domestic variety globe, you are restricted as to your watts per length of globe; ie. a 4ft globe will only come in 39w. A 2ft globe is only available in 15w (I know this because I have searched high and low). T5 and T5HO, however, is far more flexible. You can obtain various wattages for a given globe length. Also, they use less power and put out more light (PAR). There is nothing wrong with the T8's as such, you are just limited with your selection.

Agree with everyone re the CO2. At 3wpg all you will grow is algae. I promise. As to DIY CO2, it is great for learning all about how CO2 works and what might be possible, but the constantly fluctuating output of DIY will mean you are constantly battling algae. I used DIY for about 6 months...it worked OK, but going pressurised is the best thing I ever bought for my tank. Ever. I have bugger all algae issues, I am not resetting my mix every week or fortnight and my plants are loving it. Also, pressurised can be switched on and off...something not possible with the DIY and it really is a waste to have all that gas not being used... I also dose Excel as a fert and to help control what little algae that does occur.

Footnote: your tank is freaking gorgeous Peter! Lovely work!!

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The Calvin Cycle, a light-independent reaction, occurs both with (daytime) and without light (nighttime). The reaction uses CO2 from the environment. The Calvin Cycle Wiki Page

There is another link here from a plant biologist explaining photosynthesis and respiration which explains things kinda nicely.

What I am wondering is the reasoning behind turning the CO2 off at night. If it is to save your CO2 reserves then that makes sense, as plants need less CO2 at night than during the day (IIRC). If it is to prevent damage to the fish/invertebrate inhabitants, then I have found a lot of differing opinions on that. Most of the studies people cite involve commerical fishery species, which are very different from tropical aquarium species. There seems to be evidence to suggest that very high concentrations can be detrimental to fish in aquaria, but most aquarists do not have the means to test their CO2 ppm. I have found a lot of posts on planted tank forums where people have suggested that levels over 30ppm are detrimental to some species (although again there seems to be argument as to why) but that some species (specifically anabantoids) can tolerate levels up to 50ppm.

Edited by Terribletegs
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The light-independent reactions require ATP and NADPH, which are products of the light-dependent reactions. Since the turnover for cellular processes is quite high, the light-independent reactions cannot be maintained in darkness because the ultimate biological source of ATP and NADPH is the light-dependent reactions.

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Yes, you are right Stefan. :wacko:

I just asked the plant physiology professor upstairs from my lab - she said that while the Calvin cycle is independent of light, the plants would not continue this process for long after the lights went out, because like you said, the light-dependent products would run out quite quickly while photosynthesis is taking place. Unless the plants are a certain type of plants that run the calvin cycle only at night (aquatic plants are definitely not those plants).

Sorry about the thread hijack! I am going to start a new thread about CO2.

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Thanks Lisa! :)

I have been reading a lot about this today! :wacko:

The main problem people seem to suggest in leaving the CO2 on overnight is that the fish can become stressed (only if your CO2 gets too high...) and some report large fish losses, which they blame on CO2 poisoning.

The symptoms of O2 deficiency are fish hanging at the top of the tank, gasping for oxygen.

The symptoms of CO2 poisoning (in the abscence of O2 deficiency) are fish sitting at the bottom of the tank, rocking side to side.

Seeing as the 'gasping at the top' symptom is the one that people report seeing when having this problem, it seems to me that really it is not CO2 poisoning but O2 deficiency.

It's my opinion that this is probably the airspace above the water surface being displaced by CO2 that cannot escape the tank hood. This could be prevented by making sure that your tank hood is ventilated to allow any CO2 buildup to escape. I have also read that having an airstone run in the tank overnight will allow any excess CO2 to degas out of the water, preventing dangerous buildup.

All of that only really applies if you are lazy like me and don't want to turn your DIY off overnight, I guess. :rant: If I had a fancy system, I'd probably turn it off overnight. Some people suggest that the pH swing caused by doing so is more detrimental to the fish. But if Takashi Amano and Tom Barr turn their CO2 off overnight, surely it can't be that dangerous... although they are running super-fancy pH controllers too probably.

Edited by Terribletegs
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Like wise Lylarlla. Everyone interested in trying. Post back here to see how you go and we could make this a Co2 journal.

Every fortnight or so we can check back here and discuss any problems or changes in growth and what mixture we are using... Sound good?

Im making a DIY over the week end.

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For me it's the fluctuating pH caused by the CO2 which is more of a concern than the CO2 levels themselves. Ideally I want my fish to have a completely stable pH. However the pH swings which are cause by CO2 injection will vary greatly from tank to tank. There are lots of variables: amount of plants, fish, what the substrate is made of, etc. So if the fish in your tank won't tolerate pH swings the best thing is to test the pH at various times during the day and night, with CO2 on and off.

I'm not sure I would recommend turning off CO2 if you're using a DIY bottle. I haven't tried it myself but I wouldn't trust a fermenting 2L coke bottle to hold its contents. You might wake up to a nasty, smelly mess one morning. Actually it's not that smelly. Kinda smells a bit like ginger beer to me. So I guess you might just wake up to a sticky mess one morning. :wacko::rant: Whaaaaat? It's Friday. Been a long stressful week at work. Can anyone blame me for being twelve again?

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'razza, you will find fluctuating pH due to CO2 will be more prevalant in the DIY setups. Since going pressurised, pH and kH have all remained steady for me. I cannot reccomend pressurised enough....have you all had enough of me recommending pressurised yet?? No? Sweet! GO PRESSURISED!! :wacko:

Just wanted to add one thing to the OP. When drilling the hole for the airline in the bottle lid, drill approx 1-1.5mm SMALLER than the diam of your tube. Also, use silicone tubing, it is flexible and will hold tight against the hole. You will find with a hole so much smaller than the tubing, it will be VERY hard to get the tube through. This is a good thing. Just cut the tube on a very steep angle and drag it through with a pair of pliers. No need for silicone glue which WILL (guarenteed) perish and leak.

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when you are re using diy co2 over and over its best to do what lili suggested and silicon an ailine connecter into the lid, much better seal.

You can go pressurised for as little as $75 delivered to your door.

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'razza, you will find fluctuating pH due to CO2 will be more prevalant in the DIY setups.

I wasn't suggesting otherwise. I was just pointing out that swinging pH is a concern for me in relation to whether or not to turn off CO2 at night. And I'm not saying that turning it off is always the way to go. Sometimes leaving it on 24/7 provides a more stable environment. It depends on the setup. I have used DIY quite a lot in the past. The first planted tank I set up in 1995 used a DIY bottle. I'm pretty familiar with its drawbacks. I'm now using pressurised.

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Ill be siliconing the connector into the lid. That way i can replace the tubing as required.

I have made a canister out of pvc piping, Big enough to fit a 2L coke bottle in with plenty of room for expansion. By doing this i can prevent that aweful mess in the event of the bottle exploding thus decreasing the liklihood of a clean up and the odour.

Will set it up over the week end and let you know how it goes.

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What is considered excessive for Co2 in a 4ft tank. Ive been told 30 - 40 ppm is ideal. Correct?

30 or 40ppm will be 30 or 40ppm in a 2ft, 4ft or even 19ft tank... The amount of gas required to acheive that level will be the only variable.

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