CO2 Injection

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djlen

Fish?.......What Fish?
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Aug 19, 2002
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Owing to the fact that one our members recently lost a number of fish, due to improper use of CO2, I felt a need to post on this subject, regarding the dangers as well as the attributes of using gas in the planted tank.
Shortly after reading his post I was visiting another site (myfishtank.net) and read what I consider to be a very well written and thought out article on this subject by Kevin Batchelor, AKA: '1979camaro'.

Kevin's article:

While there are many different opinions about lighting, fertilization, and substrate, carbon dioxide is considered to be a necessity by most, if not all, aquascapers who are interested in creating dynamic, heavily planted environments. Certainly, success can be had without the addition of CO2, however the results will not be the dazzling aquariums which inspire so many aquarists to undertake a planted setup.

Carbon dioxide is the most critical plant nutrient (light not being a nutrient). Any stocked aquarium will provide plants with some CO2 (due to the respiration of aerobic organism, aka fish and other critters), and while this minute amount is often sufficient to maintain a few healthy plants, it can in no way fulfill the needs of a densely planted aquarium. When CO2 is not present in sufficient quantity plants grow very slowly and will tend to stay smaller. Furthermore, biogenic decalcification can occur; this is, essentially, a last ditch effort by the plants to obtain CO2 by breaking down the salts in the aquarium water. As this process occurs, the pH level can raise a couple points in a fairly short period of time. This alone is stressful enough for the fish, but the problem worsens when the lights are turned off. When photosynthesis stops at night, the plants will stop breaking down these salts and the pH will drop rapidly. This fluctuation is very harmful for the fish, but there is a simple remedy: provide the plants with a source of dissolved CO2.

So, now that the ill effects of carbon dioxide deficiency have been presented, the question becomes: how does one provide dissolved CO2? When the volume of water is large it is very difficult to supply and regulate the amount of CO2 necessary without a pressurized system and a regulator. A good analogy is a scuba divers tank. The bottle valve is always on and the regulator adjusts how much CO2 is injected into the water. This type of setup can be fairly costly, however it is certainly the most reliable means of controlling (and adjusting with ease) the amount of CO2 in the water. For small tanks, particularly those of 55 gallons and smaller, Do-It-Yourself (DIY) CO2 injection is often the cheapest solution. DIY CO2 is quite cheap. Aftermarket products are available to the person wary of actually doing the DIY themselves, however there is virtually no difference between these products and a simple DIY CO2 reactor and diffuser. The drawback to a DIY setup is the relative difficulty of adjusting the amount of CO2 injected into the aquarium. However, most people with small aquariums find that a DIY system works well, and the lack of regulation does not generally cause a problem with over-dosing. A simple DIY reactor can be built for around $10, considerably less than a pressurized system.

Building a DIY CO2 reactor is a great first project. It is relatively straightforward; all one needs is a 2L bottle, aquarium silicone, airline tubing (many people use silicone tubing because it degrades less quickly), a check valve, and something to diffuse the bubbles (cotton balls and air stones both work, as will most anything with a fine mesh; some people use a bell type diffuser). First, measure the diameter of the airline tubing (it is usually 1/4", but there are other sizes). Next, using a power drill or Dremel tool drill a hole into the plastic cap of the 2L bottle. Frequently, the soft plastic seal on the inside of the cap must be removed at this point. The hole should be just slightly smaller than the diameter of the tube to help establish a tight seal. Insert the tubing from the top of the cap into the hole until it extends at least one inch through the underside. At this point, seal around the tubing on both sides with silicone aquarium sealant. It is important to do a good job filling all the crevices and gaps or else the CO2 will leak. Read the directions on the tube to see how long it needs to fully set; a day is a good estimate, however waiting an extra night will not hurt. If the sealant is not fully cured it simply will not hold, and that can be very frustrating. At some point in the tubing many people place a check valve. This is a good precautionary measure to prevent water from siphoning back into the bottle, especially if the reactor will be below the water level; a check valve is, however, by no means a necessary component of the DIY CO2 reactor. Two or more bottles can be connected together through the use of a T connector; brass is best because it will not dissolve as quickly as hard plastic; in theory, as many bottles as are necessary can be connected together. The placement of the tube outlet is really a matter of personal choice. Many people like to put it in the filter intake because this allows the CO2 more time to mix into the water; really, anywhere in the tank will work, though lower is generally better because the bubbles will have more time to dissolve.

So, now there is a beautiful DIY CO2 reactor sitting under the tank, but it is empty. There is one general formula for creating the CO2, but there are many different opinions on the proper measurements for the ingredients. One which has been successful for many people is a combination of 3 cups of white granulated sugar, 1 teaspoon of baking soda, and 1 teaspoon of yeast. The yeast consumes the sugar which uses the oxygen in the bottle and releases CO2 as a by product of this process. Combine these three ingredients in the bottle and fill it with lukewarm water to the area where the bottle begins to slope inward. Though it is not necessary, it is not a bad idea to shake the bottle up and try to dissolve as much of the sugar as possible. All that is left is to screw the bottle into the cap and watch the bubbles begin. Usually this process takes 10-30 minutes with full strength being reached within a few hours, however do not fear if it takes a little longer. Certainly, however, if no bubbles appear within 24 hours there is a problem and any seals should be checked. Most often the escaping CO2 can be heard hissing around the area where it is leaking.

A noticeable improvement in the growth rate of the plants should be visible within a few days, however certain things can prevent the CO2 from having its full effect. The most frequent problem is surface agitation; surface movement facilitates the release of dissolved CO2 into the air. This is particularly problematic with hang on the back filters when the water level is not raised to the edge of the filter outlet. Ideally, a canister filter should be used, however many times this is not an option, nor is it truly necessary; a daily check of the water level and topping off when required should be sufficient to prevent major problems.

Maintaining the appropriate amount of dissolved CO2 is an important part of a planted aquarium. Most planted aquariums require around 1 gram of dissolved CO2 for every 25 gallons of water. By comparing the pH value of the water and the carbonate hardness (KH) as determined through test kits it is easy to derive the milligrams per quart of CO2 through the use of a simple flow chart which is available from many sources, one of which is here: http://www.aquabotanic.com/charts.htm

Carbon dioxide is still just one part of the equation; the amount of CO2 necessary varies with the number of plants, fish, and amount of lighting. Experimentation is an important part of achieving the type of planted tank which can win praise and admiration, as well as provide satisfaction to those who view it. While it may seem complicated, it really is quite accessible with a fair amount of research, forethought, and patience.

________________________________________


I will add one comment to the above:
Before contemplating the use of CO2 in your aquarium please know your water's kH. If it is not, at minimum - 3.0dH, it should be raised before injecting gas.

Len
 
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Starry

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May 15, 2002
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A few more points

Great find, Len. I vote this in as a sticky!

I'd like to add a few things:

What worked great as a seal for me is bathtub caulking. Drilled a hole in the bottle cap, pushed the airline through, and sealed all around the hole both inside and out. I've been using the same cap and line for about two years, without any leaks, ever.

I really like the Hagen ladder-type diffuser. Barely takes up and space and works like a charm. I also have an airstone at the end of the line, so the bubbles come out fine, then take their time going up the ladder.

One tsp yeast is a lot. Especially for small tanks, start with 1/4 tsp, and add more if needed. Better safe than sorry.

I also highly recommend the Jell-O recipe. It lasts longer and is more stable, slightly easing the initial burst that is unavoidable with the plain water/sugar method. Here is the recipe:
1) Mix together 2 packs of Jell-O (any flavour - all that's gonna go into your tank is the CO2 either way) and 2 cups boiling water. Mix really well until it's all dissolved.
2) Add 1.5-2 cups sugar and mix well again. Pour the mixture into a 2L pop bottle (juice bottles aren't as good, the caps aren't as air-tight)
3) Add 2 cups cold water and mix AGAIN. Make sure the sugar is dissolved and not just collected at the bottom.
4) Now stick it in the fridge overnight, until it actually turns into Jell-O.
5) In the morning, add 1/2 cup room temp/lukewarm water and 1/4 to 1/2 tsp yeast. I would suggest starting with 1/4 tsp. If you find that it's not enough, you can always open the bottle later and put in some more.
6) Monitor your pH throughout the day. The bottle should start producing CO2 within a few hours, and your pH should drop throughout the day. If it drops too low, increase surface agitation or add an airstone, and use less yeast next time. If the pH doesn't reach your target, open the bottle and add a bit more yeast.

Finally, here's my favourite CO2 chart:
http://www.thekrib.com/Plants/CO2/kh-ph-co2-chart.html

Happy plant growing!
 

Must4ng s4lly

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Jan 9, 2004
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WOW! Thanks for the information! Great article I have a 58 g planted tank that is pretty heavily loaded with fish (thus have sustained the plants fairly well) and a 75 G The plants are not growing quite as I would like tho..... I have always hesitated to use CO2 as both my large aquariums are pretty heavily populated and I don't want to kill of my fishies. They are doing great but the plants are just OK. I would like the plants to grow better.

I have good lighting and I feed my plants, so I guess they need just a bit of CO2. My PH is 8.6 Yes, very high and it needs to be lowered. I will get a Kh kit to see what that is. Prob pretty high too. We have a lot of carbonate in our water.

My question is, would a professional system be recommended for my tank size and fish load as opposed to the DIY?? what should I do after I get set up so I don't Kill the fishies other than monitoring the PH through the day??

Thanks!
 

djlen

Fish?.......What Fish?
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Aug 19, 2002
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First get a kH test kit. You're probably right about it being OK, but always be sure before injecting.
If you have the resources, I would highly recommend a pressurized system for that size tank. It's much easier to maintain a constant pH with pressurized. And once set up to the desired pH needs only periodic monitoring. I haven't had to adjust mine for months.
Here's an excellent site which includes an article on, among other things, CO2 systems:
http://www.csd.net/~cgadd/aqua/articles.htm

Len
 

happychem

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Dec 9, 2003
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http://www.aquatic-gardeners.org/Nyberg_yeast.ppt

I found the points about nourishing the yeast interesting, I've often contemplated it, my fiance works with a bunch of yeast biochmists, but none of them could provide me with more details about what's actually in their yeast media.

I'm trying out her recipe now. I'll post later if I think there's any significant advantage over the simple sugar & yeast mix. Worst case scenario, I've got a bunch of protein mix now, I'm gonna be HUGE!:D j.k.

I will add one more thing, I switched from bread to champagne yeast for this new batch. It seemed to start working right away, whereas the bread yeast took a full day to get rolling.
 

Must4ng s4lly

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Thanks for all the feedback! I got a KH test yesterday and am still looking at CO2 units. I want to be absolutly sure I get the right one that won't fluctuate my PH & KH too much. I don't want to have any little fishie funerals!
 

anonapersona

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Mar 7, 2003
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Originally posted by Must4ng s4lly
Thanks for all the feedback! I got a KH test yesterday and am still looking at CO2 units. I want to be absolutly sure I get the right one that won't fluctuate my PH & KH too much. I don't want to have any little fishie funerals!
It's not so much the equipment, but the rate you are using.

I suggest one of the All-in-One regulator/solenoid/needle valve/bubble counters, either Milwaukee or JBL, I have both. Then from the same online store, get 10' of CO2 resistant tubing. Your choice onthe diffuser/reactor -- select in-tank or out -- that depends on the room you have and your tolerance for equipment in the tank vs inline with a canister, passive diffusers are cheaper like Eheim or Hagen ladder. Order that from wherever you get the other stuff from. Locally find a 10 lb tank, more or less, depending on the room beneath the tank. Spend about $90+$10+($20 to $50 for reactor)+shipping +($75 to $90 for tank)= $210 to $225 Add a check valve maybe, and a strap to tie the tank upright. Plug and play.

That's all you really need, the pH controller is a cool gadget for folks who can keep them calibrated -- not necessary unless you are in soft water or have time and the inclination to keep them working correctly.
 

daveedka

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Jan 30, 2004
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The question that still perplexes me, and I can't find an answer in anything I read. Does one need to shut off Co2 at night? or can it be run 24/7 this will be the deciding factor in my decision of whether or not to use Co2 ever. I travel 4-5 days every week , and don't have someone to shut off my co2 every night.
 
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