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CO2 with a sump

andy

andy

Member
Joined
14 Sep 2007
Messages
283
Location
Lewes, East Sussex
Where would you diffuse CO2 when running a sump?
Straight into the tank into the flow? or
Into the return pump in the sump?
 
If you're using a traditional in-tank diffuser I would opt to insert it into the tank on the opposite end of the overflow and on the downflow section of your filter outflow. You want to maximise CO2 surface contact with the plants, so putting the diffuser on the downflow minimises the CO2 bubbles which just rise to the top of the water and leave the aquarium, and maximises the amount of entrained CO2 bubbles in your aquarium.

The downside of CO2 addition into an aquarium with a sump is that you increase the amount of time where CO2 is not in contact with plants and also you increase the air-liquid surface area (assuming it's an open top sump), thus giving the CO2 more opportunity exit the aquarium system. In my opinion you should avoid putting a diffuser anywhere in the sump as it would just lead to excess useage/waste of CO2.

You could also use in-line CO2 atomisers on the return piping (ideally as close the pump discharge as possible). I've had good experience with in-line diffusers in terms of CO2 dispersion within my tank, the down-side is that the fine mist can be visually undesirable for some people.
 
MoFish said:
I've had good experience with in-line diffusers in terms of CO2 dispersion within my tank, the down-side is that the fine mist can be visually undesirable for some people.
Click to expand...
I agree with you - the inline diffuser mist can give the tank a specific foggy look. I use one on my larger tank, and I do find that fog slightly annoying when the CO2 is on.
 
I used separate pump with reactor. I placed pump in 3rd chamber (I had 4 in total) and outflow hose of reactor right next to return pump so it immedialty takes water into the tank. Worked like a charm 🙂
 
Last edited:
hypnogogia said:
Reactor is the way to go…
Click to expand...
Nice one, haven't thought of that.

How would a reactor work with the sump? I have a TMC 4000 return pump with has lots of different flow rates. However the soft pipe from the pump to the tank is only around 12" before it is connected to hard pipe.

Any recommendations for a decent reactor make?
 
MoFish said:
If you're using a traditional in-tank diffuser I would opt to insert it into the tank on the opposite end of the overflow and on the downflow section of your filter outflow. You want to maximise CO2 surface contact with the plants, so putting the diffuser on the downflow minimises the CO2 bubbles which just rise to the top of the water and leave the aquarium, and maximises the amount of entrained CO2 bubbles in your aquarium.

The downside of CO2 addition into an aquarium with a sump is that you increase the amount of time where CO2 is not in contact with plants and also you increase the air-liquid surface area (assuming it's an open top sump), thus giving the CO2 more opportunity exit the aquarium system. In my opinion you should avoid putting a diffuser anywhere in the sump as it would just lead to excess useage/waste of CO2.

You could also use in-line CO2 atomisers on the return piping (ideally as close the pump discharge as possible). I've had good experience with in-line diffusers in terms of CO2 dispersion within my tank, the down-side is that the fine mist can be visually undesirable for some people.
Click to expand...
I agree with this,
 
I have a 29-gallon heavily planted tank with 9-gallon DIY sump. It works wonderfully.
CO2 gets injected into the return hose from the sump. I use a CO2Arts Inline diffuser and have a check valve right next to the diffuser inlet.
I've built a system that uses pH to switch my CO2 system on and off.

Things I have learned
  • Using colored liquids to measure CO2 is way too slow and inaccurate for injected CO2. I now have a submerged pH meter that takes regular pH readings to indirectly measure CO2 saturation.
  • Using a timer for CO2 results in pretty wild pH swings in the water. In my case I turned the CO2 on before the lights came on and off just before the lights turned off. I saw pH swings between 6.7 and 7.4. Some fish didn't like this. None of the shimp liked it.

I now rely on the submerged pH meter and have set a narrow range of pH - 6.85 to 6.95 - to regulate the CO2. I built this myself using Arduino on ESP32. CO2 turns on when pH is above 6.95 and turns off when pH hits 6.85. I'm sure there are commercial systems that let you do the same. pH swing is now minimal, plants are happy, fish are happy, and my shrimp are all alive and thriving. I have a little crushed coral in my sum to add hardness and measure hardness occasionally.

If you want to know more, reply to this thread.
 
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