Co2- where am I going wrong?

Abi Jones

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I have just stated adding co2 to my 126 litre tank again after giving it an overhaul with new substrate and plants. I have good flow from my filter with spray bar positioned on the right top end, the stream reaches all the way to the other side. I have co2 diffuser low down on the opposite end to the spray bar, and a power head on the back wall above the filter inlet to catch the co2 bubbles and push them out across the tank. I can see the bubbles in the water, they aren’t as dense at the end furthest from the diffuser tho. I have a drop checker each end but

neither ever goes green, and I’ve tested ph before co2 starts, again 2 hrs later just before lights come on and and again just before it goes off 10 hours later but it doesn’t change at all. I’m running 120 bubbles per minute which should be enough, can anyone tell me what I can change in my set up to improve co2 saturation? Also is there another way of testing co2?


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Zeus.

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I would lower the spraybar slightly about 1cm as a little less surface agitation will help. The filter inlet is best on same side as outlet as it helps create more circular flow. Power head is best if it complements the spraybar flow also - I would go for top right hand corner at the front of tank.

CO2 diffuser left hand side low as possible near front.

With the positioning above I have suggested, I believe the bubbles from the CO2 diffuser will travel right across the bottom off the front of the tank- which will get a better CO2 uptake in the tank.

Getting CO2 inject right is hard and needs a lot off trail and error - esp if its your first time and most folk get it wrong.

120 Bubbles per minute which is 2 bubbles per sec IMO wont get much of a pH drop on a 126l tank

Here's my BPS on 500l tank for comparison


But I am using twin injectors and one switches off once the pH drop is achieved, This injection rate is not for the faint hearted so please don't copy - the DC was yellow at lights on after 30mins

Best way of checking the waters [CO2] is the drop checker IMO, pH probe/pen is great for doing a pH profile which I would strongly advise
 

Abi Jones

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Location
Southampton
Thanks for your reply, that’s very helpful. The cut outs for the inlet and outlets are on the back wall at either end so I can’t really have them close together, I can put spray bar on the back wall also but it will still be a way away from the inlet. Unless I can fit both into one cut out but I’m not either hose is long enough to stretch that far. In your opinion is the spray bar best placed at the back or at one end?


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Zeus.

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In your opinion is the spray bar best placed at the back or at one end?

At the back off the tank -but all the way along 'ideally' - then with the taller plants at the back off the tank the water flow is upwards at the back, then the deepest part off the tank to substrate level is at front where the water flow is downwards and CO2 enhanced water is being pushed to the substrate level, so the CO2 distribution is better.
 

Abi Jones

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Southampton
Thanks so if I extend the spray bar and put it along the back wall where would be best to put the power head and o2 diffuser? Sorry for all the questions!
 

Zeus.

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Well I would put the powerhead under the spray bar in the middle at the back with the CO2 diffuser at the back with the bubbles rising so they get picked up by the powerheads input/output flow. If I had a spare timer I would also put the powerhead on it with it coming on when CO2 comes on and going off when lights go off, this would enable the clean up crew to clean the powerhead and any bits of plants/leaves to fall off it.
 

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