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Attempts to optimise CO2 distribution

MrClockOff

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20 Aug 2020
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Hi all,

Hope someone can help me optimise the CO2 distribution through optimum water circulation.
I have two pumps of the same flow rate 650l/h Eheim BioPower 200 filter and Eheim Aquaball 650 power head. Currently they are pointing in the same direction along the tank. One attached next to the back glass and another next to the front glass. See pic attached. CO2 diffuser twinstar neo is attached to opposite side of the tank. I can see bubbles travelling from diffuser down to the substrate along the front glass and up underneath the front pump. But it seems not many bubbles going along the back glass.
I wonder if the pumps would be pointing at each other but still one along the back and other along the front glass creating circular movement at the surface (vortex) and hopefully under water too..

Would moving the diffuser under one of the pumps intake improve the diffusion and distribution even better?

what are your thoughts guys?
 

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Mark Nicholls

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15 Feb 2020
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Try putting your dropchecker in different areas of the tank to see if the colour changes.
If its the same colour in each location, you have good dispersal; if not, then you have poor flow.
 

jaypeecee

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21 Jan 2015
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Would moving the diffuser under one of the pumps intake improve the diffusion and distribution even better?
Hi @MrClockOff

It doesn't look as if there's room to position the diffuser under the rear filter. And, it can cause a problem (noise) if the CO2 becomes trapped inside a filter. In the past, I have successfully positioned the CO2 diffuser a few centimetres below a small streaming pump such as the one here:


When carefully positioned, it is possible to ensure that the rising CO2 bubbles don't become trapped inside the pump itself. If I remember rightly, the Voyager Nano does not have variable flow-rate.

Good luck!

JPC
 

MrClockOff

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I thought if I wouldn’t try I wouldn’t know.. so in the end I did switch powerhead and diffuser places. Now the filter is pushing water along the back wall as before and the powerhead is pushing water along front wall but in the opposite direction. So water is circulating clockwise. The result is amazing! I have not touched my CO2 injection rate since the water circulation rearrangement which was set for 1ph drop but after rearranging water circulation and diffuser placement the drop is 1.3ph at the same BPS! Less CO2 wasted. Finally my Ludwigia palustris looking much happier 👍
 

jaypeecee

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I have not touched my CO2 injection rate since the water circulation rearrangement which was set for 1ph drop but after rearranging water circulation and diffuser placement the drop is 1.3ph at the same BPS! Less CO2 wasted.
Hi @MrClockOff

Good news on your rearrangement. You may want to consider reducing the CO2 BPS. With a 1.3 pH drop, you could be looking at a stabilizing CO2 concentration as high as 60 ppm. Your fish are almost certainly not going to be happy with that. A 1.3 pH drop is a factor of 10^1.3 = 19.95. At a starting atmospheric equilibrium CO2 concentration of 3 ppm in the aquarium water, 3 x 19.95 is a gnat's whisker short of 60 ppm.

JPC
 

SudhirR

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I thought if I wouldn’t try I wouldn’t know.. so in the end I did switch powerhead and diffuser places. Now the filter is pushing water along the back wall as before and the powerhead is pushing water along front wall but in the opposite direction. So water is circulating clockwise. The result is amazing! I have not touched my CO2 injection rate since the water circulation rearrangement which was set for 1ph drop but after rearranging water circulation and diffuser placement the drop is 1.3ph at the same BPS! Less CO2 wasted. Finally my Ludwigia palustris looking much happier 👍
So essentially the flow from the filter output pushes down the CO2 bubbles from diffuser and the power head out spreads the bubbles across the tank, yes?
 

ceg4048

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I wonder if the pumps would be pointing at each other but still one along the back and other along the front glass creating circular movement at the surface (vortex) and hopefully under water too..
Hi,
That's never going to happen. You cannot play ping-pong with water in a bathtub. In any case I fail to see a problem with this tank. I mean, it looks amazing. If you are not having any problems with plant health I see no reason to make any changes.
Would moving the diffuser under one of the pumps intake improve the diffusion and distribution even better?
Again, if the need arises then you could try that. As long as the filter doesn't object by spitting and sputtering then sure that could work. Each tank and gear is a little different and is it's own puzzle, but you seemed to have solved your puzzle. I would leave well enough alone.

Cheers,
 

MrClockOff

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Hi @MrClockOff

Good news on your rearrangement. You may want to consider reducing the CO2 BPS. With a 1.3 pH drop, you could be looking at a stabilizing CO2 concentration as high as 60 ppm. Your fish are almost certainly not going to be happy with that. A 1.3 pH drop is a factor of 10^1.3 = 19.95. At a starting atmospheric equilibrium CO2 concentration of 3 ppm in the aquarium water, 3 x 19.95 is a gnat's whisker short of 60 ppm.

JPC
Almost week since the change and fish and shrimps all looking fine. Monitoring them every day. I’m going to reduce injection back to 1ph drop once I’ve got new precision needle valve as the generic one is a nightmare..
 

MrClockOff

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Hi,
That's never going to happen. You cannot play ping-pong with water in a bathtub. In any case I fail to see a problem with this tank. I mean, it looks amazing. If you are not having any problems with plant health I see no reason to make any changes.
I do agree but after rearrangement I got it very close to what I was looking for. The water at the surface is mowing now in the circular way and the CO2 bubbles are moving the same way under the water. So now I see bubbles at the back and front. I had tiny issue with Ludwigia palustris. When it was getting closer to the surface the tips were starting degrading like new growth was dying. I already reduced light intensity but that was not enough. I had to push those CO2 bubbles somehow towards Ludwigia.

here is the new arrangement btw
 

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MrClockOff

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So essentially the flow from the filter output pushes down the CO2 bubbles from diffuser and the power head out spreads the bubbles across the tank, yes?
Yep, something like that, powerhead pushes bubbles down to the substrate and everything what is raising up is picked up by either powerhead or filter flow and pushed further along the tank.
 
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