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CO2 Question...

3K views 15 replies 6 participants last post by  klosxe 
#1 ·
28 Gal, 5 plants, 1 is bamboo, 1 is bacopa(?), don't know the rest. I just set up DIY CO2 and am wondering if anyne might know what a good bubble per minute rate would be?? Right now I'm getting about 20 bpm, it's only been going for about 16 hrs, so it might speed up a little, we'll see. Anyway, any insight would be helpful, thanks!
 
#3 ·
A good indicator of CO2 levels with DIY CO2 is your PH levels. If you have a PH in the range of 6.5-6.8, you are adding the right amount of CO2. If PH goes up, that means that your CO2 levels are getting lower, and vice versa. I would put in a control valve, so that you can turn on/off you CO2 and change the BPM (Bubbles per minute) rate. You should aim at 2-3 Bubbles per Second, or 120 BPM. At night, you should turn off your CO2 because the plants USE oxygen at night when they aren't photosynthesizing. Plus then at night your PH will rise naturally, and in the morning when your lights come on, you can turn you CO2 on, and the PH will slowly fall. You will want to insert a control valve so that you don't over inject CO2, and drop PH too low, and vice versa.

My next tidbit of Info depends on your answer to my next question: Do you have a tight budget, or can you invest some $$ into this tank?

If you can spend some $$, I would invest on a full auto CO2 system. Full Auto means that the system monitors PH levels, and when PH is high, CO2 is turned on. When PH is low, CO2 is turned off and allowed to rise natural. AquariumPlants.com has a great system that I use. This is a little pricy though, but I think it is worth it. If you ever want a bigger tank, this can just be moved over. When your CO2 tank is low, you can take it into a welding shop and they will refill it for you for about 40 $. You only need to refill about ever 8-10 months though. This is the way to go, because the injection system will monitor itself, and you don't have to worry about injecting too much CO2 and dropping the PH too low, and vice versa.

If you plant to stick with DIY, I would definitely find a way to insert some kind of control valve so you can control you BPM. Hope this LONG explanation helps. :)
 
#7 ·
Plants can and do take up some CO2 at night and store it for use in the process when the lights come on. Some plants have evolved to the point where they only take in CO2 at night. Yes it is true and no I didn't believe it when I first saw it either. As far as I know there are no aquatic plants that do this but even aquatics can and do take up some CO2 at night for use during the day.

The biggest reason, especially with DIY is because you can have massive pH swings that can kill your fish by starting and stopping it all the time. This can hopefully be taken care of by having a good KH but the risk is high. That is why so many get a pH controller for pressurized systems.

When I used DIY CO2 I never stopped it and did my best to keep the levels steady at all times, even at night. Fluctuating levels of CO2 can be worse than not using at all. I know, been there. My levels would fluctuate simply from temperature changes in my house and it caused more algae than it helped plant growth especially in fall and winter.
 
#8 ·
??? What other rescource can you provide to back up your statement??? Plants only use CO2 during the process of photosynthesis. I've never, in my 30 years in the aquarium hobby, ever heard that CO2 is absorbed during the night. I would greatly appreciate some hard evidence to support your statement, which, I personally feel, is incorrect. I am aware that some plants do take in CO2 only at night, but that percent of aquatic plants is miniscule at best. In the natural world, the PH Naturally flucuates from night to day as I described earlier. Isn't the point of an aquarium to provide a slice of that natural world in your home?
 
#9 ·
http://www.fishforum.com/viewtopic.php?t=10471&highlight=photosynthesis

The Calvin part of photosynthesis happens continually, day and night. Plants take up CO2 all the time with or without light. The uptake of carbon from CO2 happens all the time so turning off the CO2 at night only leads to pH swings and weaker plants that have to work harder because they did not store up enough nutrients when they could at night.

Like I said, I do not know of any aquatic plants that only take up CO2 at night but they will take it up all night long and this being the case, the more nutrients they can store, the more efficient they will be when they can complete the light dependant part of the cycle.

Might be why most who inject CO2 will leave the systems if they know that it will not harm the fish.
 
#10 ·
I had contemplated using such a system (DIY) to introduce co2 into a ten gal. tank a year or two ago. I was under the impression that one should never attempt to block or restrict the flow of these do it yourself units as co2 is constantly being produced. As I understand it, A rather nasty mess can be a consequence of doing so. I agree with Fish-4-all that shutting off co2 of an evening would result in larger and more sudden PH swings which would be harmful to many fish.
 
#12 ·
The problem with putting a control valve and potentially even completely stopping the flow of co2 in a DIY system is that you will EXPLODE your co2 generators! Just because you stop the flow of co2 into your tank does not mean that the co2 is not being produced in your plastic bottles or whatever you're using. You may be able to slightly restrict the flow for a little while but you will still be backing up the co2 in your generator and will have to eventually let it out to avoid explosion. If you want to control the amount of co2, purchase a compressed system. Unless you have a larger tank a DIY system is fine if you don't mind the maintenance. If you restrict or stop the flow you will end up with a big giant mess.

A possible solution is creating something like a storage container to store that excess co2 while your lights are off, but you would still need to ensure that all of that co2 was evacuating before the end of each day otherwise you are still going to end up with an explosion at some point.
 
#13 ·
I'm about to implement a DIY system pretty soon. After doing some research here are some interesting things you could do to help the process.

First, and this in my opinion is most important, if you use a tee valve to seperate your tubing between your generator and reactor then sand down the exposed end and attach a rubber cap you can create a makeshift pressure release valve. This way if the co2 does get backed up the cap will blow off releasing the pressure rather than blowing your tubing (or worse). Should be pretty easy to implement in a DIY system that is already established. Just cut your tubing and insert the tee valbe.

Another thing I found was a different way to diffuse the co2 in your water. Using a cheap water pump, connect the pump (with a prefilter) to a cheap gravel vacuum (the plastic tube). This will force the water to mix with the co2 while also preventing the gas from escaping. It also suggests using an airstone at the end of your tubing, but these will likely degrade pretty fast.

Here's the source I was reading. http://www.qsl.net/w2wdx/aquaria/diyco2.html

If you're looking just to increase the flow, slap another generator on there.
 
#14 ·
You can also use an air pump with an airstone in your tank to bleed off excess co2. Some people run them for a few hours at night on a timer. The only time I've been concerned about too much co2 in the tank is during the first 24 to 48 hours of adding the yeast to the mixture. This is the time when the yeast is the most active. So to bring the levels down a tad I have turned on the airstone for a few hours at night. Just be careful about messing with the co2 levels too much, as large changes in co2 can cause large PH swings which might affect any fish you have (if any). After 48 hrs the flow of co2 becomes rather stable for about two weeks.

If you find that after 48 hrs the co2 is still bubbling in too fast then make a mixture with less yeast. Less yeast = less co2 production. One bubble every 3-4 seconds seems like a good start point. It will take some experimenting to find the right receipe for your tank.

But what ever you do, NEVER EVER restrict or shut off the outlet tube of your DIY co2 generator! KABOOM! A blow off device is a good idea, but again, it will take some experimenting to find the right blow off pressure.

Good Luck!
Doug
 
#15 ·
Absolutely Doug. Even just restricting the flow could result in disaster. As kids we used to take the heater powder from my dads old MRE's and throw them in a 2 liter bottle with some water and shake it up. As you said...KABOOM! The same effect would happen with the co2 if the flow is stopped.
 
#16 ·
While I do agree that stopping the CO2 flow COULD be bad, I had used control valves on my DIY for YEARS, and I have NEVER had anything explode. I would agree with you that you shouldnt restrict the flow, but I personally have never had any such problems.
 
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