Best location for Co2 outlet into a long tank - The Planted Tank Forum
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post #1 of 19 (permalink) Old 06-26-2010, 01:54 AM Thread Starter
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Best location for Co2 outlet into a long tank

Hi everyone, I recently set up a 6 ft 100 gallon long tank and wondered if there is an ideal location where the Co2 should be discharged into the tank? At the moment it enters the tank at one end exiting through a spray bar. Filtration is Eheim 2217, Eheim 2028 and a Rena XP3. It is being diffused in a AquaMedic 1000 reactor plumbed into the 2217. I have the BBS set around 4 or thereabouts. My kH is 12 and gH is extremely high here. I keep the pH at 7.1/7.2 via a controller. The reactor is doing a good job of totally dissolving the Co2 but I am concerned that it could be getting trapped in one end of the tank.
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post #2 of 19 (permalink) Old 06-26-2010, 01:58 AM
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as long as you have enough flow, which it sounds like you do, your fine
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post #3 of 19 (permalink) Old 06-26-2010, 01:59 AM
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do you have a drop checker?
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post #4 of 19 (permalink) Old 06-26-2010, 02:15 AM Thread Starter
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Yes, I placed the drop checker at the opposite end of the tank and it is dark green.
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post #5 of 19 (permalink) Old 06-26-2010, 03:09 AM
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well, you have a ph controller, is the ph different on the other side of the tank?

i would probably up my co2 a little bit more to get it more light green.

it should be fine. i wouldnt worry. you have more flow and filtration that most people
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post #6 of 19 (permalink) Old 06-26-2010, 02:01 PM
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4bps on a tank that size is not very much. Considering the surface area, you lose a good deal of co2.
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post #7 of 19 (permalink) Old 06-26-2010, 04:18 PM Thread Starter
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Quote:
Originally Posted by over_stocked View Post
4bps on a tank that size is not very much. Considering the surface area, you lose a good deal of co2.
I'm curious if you would you still think this way if I told you our local waters pH is 8.1 out of the tap and I am not using RO water or anything other than Co2 to lower the pH.
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post #8 of 19 (permalink) Old 06-26-2010, 04:22 PM
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dont get hung up on what the ph is. you need to worry about what the co2 level is. sounds to me like you're trying to follow the ph/kh chart
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post #9 of 19 (permalink) Old 06-26-2010, 04:35 PM
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A 6 foot long tank is very hard to get uniform distribution of CO2 in, with only a single input point at one end of the tank. I think most people with that long a tank use two input points. If you were using a CO2 mist method for supplying CO2, you could at least see where the CO2 goes, and that method is very effective at getting CO2 to the leaves where it is needed. But, if seeing all of those bubbles swirling around in the tank bothers you it isn't the best choice.

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post #10 of 19 (permalink) Old 06-26-2010, 10:17 PM Thread Starter
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Originally Posted by timwag2001 View Post
dont get hung up on what the ph is. you need to worry about what the co2 level is. sounds to me like you're trying to follow the ph/kh chart
Yes, that is what I have been following. Is there another preferred method I should think about? I doubt with my high kH I can do much better than I am really?
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post #11 of 19 (permalink) Old 06-26-2010, 10:20 PM Thread Starter
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Quote:
Originally Posted by Hoppy View Post
A 6 foot long tank is very hard to get uniform distribution of CO2 in, with only a single input point at one end of the tank. I think most people with that long a tank use two input points. If you were using a CO2 mist method for supplying CO2, you could at least see where the CO2 goes, and that method is very effective at getting CO2 to the leaves where it is needed. But, if seeing all of those bubbles swirling around in the tank bothers you it isn't the best choice.
Yep the bubbles would be an eyesore. So you're talking about a having a twin manifold perhaps?
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post #12 of 19 (permalink) Old 06-26-2010, 10:53 PM
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kh/ph relationship table assumes that you dont have any other buffers in your water other than carbonates. for instance phosphate buffers will throw the table off.

2 co2 outputs would be a good idea, but..
i still think that you have enough flow with the three filters to get your co2 around but i still think you need to increase your co2..
however hoppy definately knows more than i do.
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post #13 of 19 (permalink) Old 06-27-2010, 01:19 AM Thread Starter
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Quote:
Originally Posted by timwag2001 View Post
kh/ph relationship table assumes that you don't have any other buffers in your water other than carbonates. for instance phosphate buffers will throw the table off.

2 co2 outputs would be a good idea, but..
i still think that you have enough flow with the three filters to get your co2 around but i still think you need to increase your co2..
however hoppy definitely knows more than i do.
Well, there are no other buffers in my tank water other than whatever the local city water supply comes with. Armor stone (inert) and 3 large pc's of Malaysian driftwood. This why I thought using the kH/pH method for Co2 would be reliable in my case. Substrate is Flourite black. I have lowered the setting on my pH controller a little bit and we'll see where things stand as far as the color of the drop checker.
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post #14 of 19 (permalink) Old 06-27-2010, 01:52 AM
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Does your drop checker have 4 dKH water in it, made from distilled water with a tiny amount of sodium bicarbonate in it? If it has tank water it just measures the tank water pH, which is a poor way to do that. Anything in the water that affects the pH will make the pH, KH, CO2 table incorrect, usually making it indicate much too high. Even driftwood can slightly lower the pH. A substrate that has a high CEC can also affect pH, by adsorbing the + ions.

One way to get two input points for CO2 is to use a needle wheel pump to chop up the CO2 bubbles very finely, so they mix and get dissolved in the water easily, then have it discharge at two locations in the tank. Another way would be to split the CO2 line so about half of the CO2 goes to a diffuser at each end of the tank. The challenge is to get CO2 rich water to the farthest point in the tank, before the CO2 is lost from the water surface, or used up by the plants. Obviously the longer the tank, the more difficult it is to do that.

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post #15 of 19 (permalink) Old 06-27-2010, 03:31 AM Thread Starter
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Quote:
Originally Posted by Hoppy View Post
Does your drop checker have 4 dKH water in it, made from distilled water with a tiny amount of sodium bicarbonate in it?

Yes I am using 4dKH water with the correct amount of sodium bicarbonate. I think it is 3 or perhaps 4 drops of the Co2 regent that I am adding to the drop checker. I must confess this regent came from China. The 4 dKH water was created locally here in my town. I read someplace that I can either buy or create my own Co2 regent? Do you think this would be a wise choice?

If it has tank water it just measures the tank water pH, which is a poor way to do that. Anything in the water that affects the pH will make the pH, KH, CO2 table incorrect, usually making it indicate much too high. Even driftwood can slightly lower the pH. A substrate that has a high CEC can also affect pH, by adsorbing the + ions.

One way to get two input points for CO2 is to use a needle wheel pump to chop up the CO2 bubbles very finely, so they mix and get dissolved in the water easily, then have it discharge at two locations in the tank. Another way would be to split the CO2 line so about half of the CO2 goes to a diffuser at each end of the tank. The challenge is to get CO2 rich water to the farthest point in the tank, before the CO2 is lost from the water surface, or used up by the plants.

The Co2 is getting completely mashed inside the AquaMedic 1000 reactor. I could look at plumbing in a T fitting on the output but I would have to make sure that both lines are equal length. For the interim I am going to move the current output so it flows along the front of the tank where there are no obstructions. From there the other filters output can swirl it around.

Obviously the longer the tank, the more difficult it is to do that.
What do people with long tanks do now? Thank you for your continued help folks.

Last edited by Philster; 06-28-2010 at 01:37 AM.
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