CO2 - rippling up AND OUT of tank? - The Planted Tank Forum
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post #1 of 7 (permalink) Old 08-13-2014, 05:45 PM Thread Starter
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CO2 - rippling up AND OUT of tank?

Hello Forum friends!

I have a pressurized CO2 setup (inline diffuser off a canister filter) and am curious whether any CO2 is actually being diffused into my tank. I was told to point my filter "in-tubes" up, which is to say, towards the water line. The idea, as I understand it, is to create a rippling surface to aid gas exchange and reduce the risk of CO2 poisoning for my fish.

My question, then, is how much CO2 is actually diffusing into the water column of my tank? Am I simply shooting CO2 back into the atmosphere or is some actually getting into my tank? I can never get those drop checkers to work...

Thanks much. Cecile
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post #2 of 7 (permalink) Old 08-13-2014, 07:20 PM
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Depending on how you feel about the drop checker failing to work, it may be giving you the answer.
Drop checkers are pretty simple items but the fluid used can be a real question if we don't know for sure that it is mixed right. Depending on commercial mixes can make us doubt the results so I do my own. If you have 1/8 teaspoon measures, sodium bicarbonate and distilled water, it is cheap to make. Recipe is on hand if you need a copy?

My way to find what is going on would be to operate on both issues. First I would get a drop checker and fluid that I felt was right. I would turn the input line down so that the Co2 is going into the water. Do this at some time when you are going to be home to watch the fish. Don't increase CO2 without watching the fish. If they begin to act strange in any way like going to the surface, less activity or not eating normally, back off the CO2 and do a bit of water change to help them. Take about a week or more of slowly increasing CO2 and at some point you will reach a point where the drop checker changes color or the fish no longer adapt to the new amount. At that point you will know you are at the max for your tank.
Turning the input up seems like a pretty weird way to go about limiting the amount you are getting in the water! Most use a needle valve to do that. Kind of like jacking the car up to limit speeding tickets? Works but it is missing some of the finer points.

Last edited by PlantedRich; 08-13-2014 at 07:22 PM. Reason: add
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post #3 of 7 (permalink) Old 08-13-2014, 09:01 PM
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Drop checker would be a good start. If you have your Co2 turned off at night, and If your normal ph is at least 7 without Co2, color should be blue by morning, then drop checker should turn green-lime green after 2-3 hours after Co2 has been turned on. If not, increase the Co2 bubble rate by 1/2bps and wait a few hours to make a difference. Surface agitation can cause loss of Co2, but if it's just a ripple effect, it's should dissolve effectively in the tank.
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post #4 of 7 (permalink) Old 08-13-2014, 09:31 PM
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I know everyone has pointed this out but drop checker would be be the first step. You could also use visual cues to see if the co2 is diffusing properly. Since you mentioned that it is an inline diffuser you should visually see the bubbles coming out of your outflow portion of the canister filter. In my tank I see little micro bubbles all over the place. Also look at the underside of the leaves of your plants, you should see that little oxygen bubbles are being produced from your plants (wait for the co2 to turn off and only lights to be on to make sure oxygen is being produced).
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post #5 of 7 (permalink) Old 08-14-2014, 04:01 AM Thread Starter
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Thanks everyone. Okay, I will try the drop checker again. For some reason, I couldn't get it to turn any color at all! I bought the correct fluid online but no luck. Will try though. Thanks!

Also, as for the ripple idea, I got that in response to my post from some time ago My discus were acting CO2 poisoned and many helpful folks pointed me to the need for more gas exchange at my tank surface. If I point the in-flowing water downwards, I get no ripple at all. Is that alright?

I've got this feeling that now I'm barely injecting any CO2 at all. I don't see the little bubbles under plant leaves nor how they're being barreled about the tank... (as you describe). Darn...

Thanks for your help!
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post #6 of 7 (permalink) Old 08-14-2014, 05:38 PM
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Some sources for the drop checker base line solution and even the indicative solution are better than others. My first experience was the same as yours, no color change at all. Then I paid a bit more and got presumably a better quality solution and used my own indicator from a PH test kit. I also found that putting a little less indicator in it helps to see the color change better, 2 drops instead of 3 or 4 work for me.
Try the diffuser on the canister's inline as you'll get better mixing on the CO2 than if it is on the outflow (by the way inline to me means in to the canister, not in to the tank).
Creating surface ripples creates more surface area and thus speeds up gas exchange between the water and air, either in or out. The main factor determining gas exchange however is the relative difference between how many molecules exist in one medium versus the other. Put simply the higher the concentration of CO2 in the water versus the air will cause a faster gas exchange. When you want the CO2 in the water to be high then you don't want a fast gas exchange to the air. When the lights and CO2 shut off then yes you want a fast exchange to take place reducing the CO2 and maximizing the available oxygen.
I have found the best and most efficient method of achieving this is with a tank lid. The lid allows for the air under it to become saturated with CO2 and thus little of the gas will escape the water once it is in solution. It then takes very little gas to create and maintain a high level of CO2. The better the seal of the lid the more efficient the process. Of course when you want the CO2 to off gas you have to help it and I use an air pump and a couple of air stones running on a timer to do this. It is a quick and efficient method of lowering the CO2 and ensuring a good supply of oxygen for the low/no light period.
So I don't concern myself with surface ripples as they are irrelevant to my set up either way.
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post #7 of 7 (permalink) Old 08-14-2014, 11:12 PM
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Rather than order and trust others to get the correct 4DKH fluid, I find it works to make my own.

The following is from a forum somewhere and I should give credit to somebody but I have lost that info way back.
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