Turning off co2 at night?

[James2009]

Hello,

I'm just recently new into the planted tank thing. I have 165 watts on a 55 gal T12's and co2 injected by way of tank and diffuser. Now I believe I have gathered almost all the information with the exception of one much debated topic.

DO I LEAVE THE CO2 RUNNING AT NIGHT OR IS IT BETTER TO SHUT IT DOWN WITH THE LIGHTS. I have an all in one bubble counter that I am able to have on a timer with the lights.

Please help, as it seems each individual person I talk to has a different opinion.

Thanks.

[Drydock]

I leave mine on, others use a solenoid and hook it to their light timers... I think you are going to get a lot of different opinions. Do what works for you.

[cale262]

I leave mine on in one tank, and the other is on a timer with the lights...The tank that has the co2 on 24hrs is growing crazy, my newly added HC has doubled in less than a week,...I may just keep it on in both tanks for a while and see what happens :shifty:

[aquatica]

Hello,

Your question regarding C02 is actually a very simple one to answer.

During the daylight hours C02 is "consumed" be the plants during photosynthesis as they in turn expire oxygen in the process. With plenty of lumen's (light) on the aquarium and fertilizer the addition of C02 put the plants into there element. But during the night cycle the reverse process takes place, so the plants actually use up oxygen in the water and aspirate CO2. Which is usually not a great problem unless you also keep fish. Leaving the C02 on during the darkness actually aphixiats the fish, because the fishes are trying to find some oxygen in the water column as are the plants and all they can find is C02. Thus a slow aphyixsiation takes place and the only thing that saves them is the timer turning the lights on in the morning. If you see your fishes in the tank hovering at the surface gasping for air early in the morning, this would be why.

C02 running 24/7 is not only a waste but it is bringing your fishes to a near death experience on a nightly basis and it is only a matter of time before some will succumb to this nightly be rage. This process happens to the fishes "best" when the tank is well or heavily plant.

Hope this helps with your question.

Timers are about 15 bucks, well worth the money!

R

[werner]

Leaving the C02 on during the darkness actually aphixiats the fish, because the fishes are trying to find some oxygen in the water column as are the plants and all they can find is C02. Thus a slow aphyixsiation takes place and the only thing that saves them is the timer turning the lights on in the morning.

CO₂ does not displace O₂ in the water. As long as you have sufficient aeration in the tank, the excess CO₂ will escape to the atmosphere and enough O₂ can be absorbed for the fishes and the plants.

Having a timer turn on a small powerhead or airstone is good if you can't/don't want to use a solenoid to turn off the CO₂.

[James2009]

Thanks for the information. The only concern I had with turning the co2 off at night is the Ph swing it could cause. However it sounds as if that would be far easier on the fish, then having to much co2 in the water.

[jvision]

The reason Cale262 is seeing such great growth by leaving it on all night is that the plants get to start the day with all the CO2 they need. Many people who do turn the CO2 off at night, start it up about an hour before lights come on again. That way plants don't have to wait for CO2 to get to necessary levels for top production.

And, the reason he isn't seeing any problems with his fish is for the reason Werner described. When plants receive all the CO2 they need, they will actually saturate the aquarium with O2 - there's plenty in there to last the night. And, since the plants start in top production mode as soon as lights come on, they start producing top amounts of O2 right away.

[catshanon]

The reason Cale262 is seeing such great growth by leaving it on all night is that the plants get to start the day with all the CO2 they need. Many people who do turn the CO2 off at night, start it up about an hour before lights come on again. That way plants don't have to wait for CO2 to get to necessary levels for top production.

And, the reason he isn't seeing any problems with his fish is for the reason Werner described. When plants receive all the CO2 they need, they will actually saturate the aquarium with O2 - there's plenty in there to last the night. And, since the plants start in top production mode as soon as lights come on, they start producing top amounts of O2 right away.

Super explanations :thumbs: Now I have to do some experiments with my CO2 and hopefully I will have a spike in growth...Just have to make sure that the tanks are heavily planted, though..so that Oxygen is being produced abundantly....

[werner]

The only concern I had with turning the co2 off at night is the Ph swing it could cause.

Small pH swings occur in nature too- not a big deal for the fish.

[thedarkstar]

The only concern I had with turning the co2 off at night is the Ph swing it could cause.

Small pH swings occur in nature too- not a big deal for the fish.

I suppose that also depends on what type of fish you have as well.

[jvision]

The only concern I had with turning the co2 off at night is the Ph swing it could cause.

Small pH swings occur in nature too- not a big deal for the fish.

I suppose that also depends on what type of fish you have as well.

There aren't many fish in the world that don't experience pH swings, since pH can be affected by just about anything including temperature. The Rift Lakes, for example, can see pH differentials of almost a full point in different parts of the lake at different times of the day.

That's why, even though collection literature says that certain Tanganyikan cichlid was collected at pH of 8.2, but they breed no problem in Edm tap water at pH 7.6.

[darkangel]

Hello,

Your question regarding C02 is actually a very simple one to answer.

During the daylight hours C02 is "consumed" be the plants during photosynthesis as they in turn expire oxygen in the process. With plenty of lumen's (light) on the aquarium and fertilizer the addition of C02 put the plants into there element. But during the night cycle the reverse process takes place, so the plants actually use up oxygen in the water and aspirate CO2. Which is usually not a great problem unless you also keep fish. Leaving the C02 on during the darkness actually aphixiats the fish, because the fishes are trying to find some oxygen in the water column as are the plants and all they can find is C02. Thus a slow aphyixsiation takes place and the only thing that saves them is the timer turning the lights on in the morning. If you see your fishes in the tank hovering at the surface gasping for air early in the morning, this would be why.

C02 running 24/7 is not only a waste but it is bringing your fishes to a near death experience on a nightly basis and it is only a matter of time before some will succumb to this nightly be rage. This process happens to the fishes "best" when the tank is well or heavily plant.

Hope this helps with your question.

Timers are about 15 bucks, well worth the money!

R

I leave my Co2 running 24/7 at 6 bbls/sec. w/3watts per gal of light. My tank is 72 gal. and 90% planted with about 50 fish 1 to 4" long. I have had no problems in the last 2 years with the exception of 1 guppy 3 days ago that most likely died of old age. This also keeps my ph at 5.5-6. However, this works for me but may not work for others.

[aquatica]

The reason Cale262 is seeing such great growth by leaving it on all night is that the plants get to start the day with all the CO2 they need. Many people who do turn the CO2 off at night, start it up about an hour before lights come on again. That way plants don't have to wait for CO2 to get to necessary levels for top production.

And, the reason he isn't seeing any problems with his fish is for the reason Werner described. When plants receive all the CO2 they need, they will actually saturate the aquarium with O2 - there's plenty in there to last the night. And, since the plants start in top production mode as soon as lights come on, they start producing top amounts of O2 right away.

I would disagree with your point about the plants not waiting for the C02 and thus get growing faster in the morning. No one I know rolls out of bed eats a couple of steaks and a few potato's and then does a marathon before lunch. If the plants truly need all that C02 first thing in the morning you should see pearling* happening within the first 1/2 hour of the lights being on when in fact it usually doesn't start till the lights have been for at least an hour or even 3. Just like human behavior we get up have some coffee breakfast and then we go to work and start working. I'm sure the plants work much the same some even show the "behavior" of not fully unfolding there leaves until an hour into their timer driven day

Even in nature the full intensity of sun is in the middle of the day when it is directly overhead which is when most of the aquatic plants are doing the greatest amount of actual growing. The rest of the day light is at best somewhat subdued or diffused coming thru bush or other vegetation

*Pearling is the giving off of oxygen by the plants during photosynthesis

R

[Baos]

There is no such thing as ph shock, it's a myth. Some lakes in nature have been recorded to move 2 ph in a day. The bigger concern is osmotic shock.

[werner]

Even in nature the full intensity of sun is in the middle of the day when it is directly overhead which is when most of the aquatic plants are doing the greatest amount of actual growing.

Although respiration is used for metabolic processes both day and night, during the day plants are much more strongly geared towards photosynthesis and storing the energy they produce from light. It's during the night that plants use this energy store for growth spurts.

I think the "steak, potatoes, and marathon" analogy is going a little overboard with the anthropomorphism. My plants are really lazy and wouldn't do a marathon to save their lives... although some do send out runners occasionally! -roll-

Pearling is dependent on the rate of photosynthesis. Slower photosynthetic rates mean that the O₂ produced by the plant is readily absorbed into the water. With rapid photosynthesis, you have a large amount of O₂ production inside the plant and bubbles form before it can dissolve in the water. Usually this coincides with the water becoming O₂ saturated.

Even if you're providing CO₂ right away, it will still take some time to see pearling. However, more readily available CO₂ (even for an extra hour a day) should result in more photosynthetic activity and therefore more energy storage and greater growth.