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Adding Oxygen at Night

Barry Hannah

Member
Joined
5 Jun 2019
Messages
39
Location
London
Seen a few people that run an air pump with a diffuser in the tank to add Oxygen in throughout the night when the lights are off.

Any one on here do the same, does it help much with the tank?

Just wondering if it's something worth looking into?
 
I’ve done it in the past when I last had a planted tank going, becasue plants use up oxygen when it’s dark.
Did it make my tank better? I don’t know, I’m sure the fish and plants were happy. But I can’t see it being an absolute necessity.

Some people just move their outlet up for more surface movement.
 
Hi all,
Seen a few people that run an air pump with a diffuser in the tank to add Oxygen in throughout the night when the lights are off.
Often it is people who use CO2 and it reduces CO2 levels back to ambient levels, once the lights are off. <"More oxygen"> is never a bad thing, so I don't really see a downside to it.
becasue plants use up oxygen when it’s dark.
They do, but a lot of that oxygen comes from the <"internal spaces within the plant"> and plants are massively net oxygen producers. If you don't have any plants then it is <"always night">.

cheers Darrel
 
... does it help much with the tank?
I strongly believe it helps a lot.
I'm a low-tech guy, yet I'm trying keeping even difficult or problematic plants. Not always successfully, I admit, but I had to try many things to learn.
In a way, we can say that plants are permanently growing and dying at the same time. CO2 injection increases growth, so it's beneficial. My strategy is not to enhance growth but to slow down dying - dropping old leaves, melting, etc. In that, I've found keeping oxygen level high the very most important thing. Permanent (24 h. a day) aeration, forcing the water to move gently, and keeping dissolved organics as low as possible is my way. Many people would say that I'm lowering the level of CO2. That's probably largerly (except in the afternoon) correct, but low level of carbon dioxide does not kill the plants. Low oxygen does.
 
... plants use up oxygen when it’s dark.
Unlike photosynthesis, plants respire permanently, day and night. Of course, while photosynthesizing they can use the oxygen they're creating.
... a lot of that oxygen comes from the <"internal spaces within the plant">
I've read multiple scientific papers which say differently. As a rule, plants respire all their own oxygen within minutes after dark. There are exceptions, though. Egeria densa can keep oxygen up to four hours after sunset. Logically, it follows that it contributes less to oxygenation of the tank during day - it "saves" oxygen for itself.
 
I run the air bubbler every night for 6 hours to reduce CO2 and increase O2 levels, I don't know if the plants get enough O2 though, as the air we breathe is mostly Nitrogen.
Main reason I'm doing this is because the outflow is not high enough to agitate the water surface. That set up is temporary though.
 
Hi all,
I've read multiple scientific papers which say differently. As a rule, plants respire all their own oxygen within minutes after dark.
I'm not a plant physiologist, or anatomist, but I'm pretty sure that is wrong and you need to "show us the money". This is a transverse section through the root of a Lotus (Nelumbo sp). and I think that it is going to take a fair while to deplete the gas (either CO2 or O2) in those vessels.

Lotus_root.jpg

By FotoosRobin - originally posted to Flickr as Lotus root, CC BY-SA 2.0, File:Lotus root.jpg - Wikimedia Commons

cheers Darrel
 
Hi all,
I've struggled to find many references. There are thousands for mechanisms for storing CO2, and for oxygen dynamics in flooded terrestrial plants, but not many specifically for oxygen storage in aquatic plants. I'd guess partially this is because where back into <"shades of grey">, where you have the complex interaction between the (dissolved) gas levels of plants, water and sediment.

I think we both agree that high levels of oxygen saturation within the water column are an unalloyed good thing. What is unequivocally true is that photosynthetic organisms "plants" are <"massively net oxygen producers">.
.... The light-induced oxidation of water by Photosystem II (PS II) of higher plants, algae, and cyanobacteria, is the main source of atmospheric oxygen......
That looks on the money, the Sand-Jensen paper (that you've highlighted) definitely suggests that the obligate aquatic marine monocotyledon Zostera marina (Eel Grass) only stores very minimal amounts of oxygen. The rest of <"Underwater Photosynthesis and Internal Aeration of Submerged Terrestrial Wetland Plants"> is really a paper about cereals that have been submerged by flood water, so most of it isn't that relevant to us.

The 2005 paper cited is:
SAND-JENSEN, K, PEDERSEN, O, BINZER, T & BORUM, J (2005) <"Contrasting Oxygen Dynamics in the Freshwater Isoetid Lobelia dortmanna and the Marine Seagrass Zostera marina"> Annals of Botany 96:4 pp 612 - 623
It is actually a paper that gets a mention on UKAPS, because the other species used was <"Lobelia dortmanna">. In the 2005 paper, for L. dortmanna it says:
Conclusions
The build-up of O2 in the pore-water of L. dortmanna sediments during the day as a result of high release of photosynthetic O2 from roots and low O2 consumption of sediments means that sediment, aerenchyma and water are important O2 sources for respiration during the following night, while Z. marina relies on the water column as the sole source of O2 because its sediments are anoxic...........
A subsequent paper: Pedersen, O., Colmer, T., Garcia-Robledo, E & Revsbech, N (2018) <"CO2 and O2 dynamics in leaves of aquatic plants with C3 or CAM photosynthesis – application of a novel CO2 microsensor"> Annals of Botany 122:4 pp 605 - 615 says:
..... Leaf tissue pO2 dynamics in Lobelia dortmanna largely followed the opposite pattern of that for pCO2 in its tissues; pO2 was slightly above air equilibrium at the end of the light period and then declined throughout the entire dark period without reaching a new quasi-steady state so that the leaf tissues were severely hypoxic (approx. 1 kPa) towards the end of the dark period ........
So inconclusive, but also suggesting that Lobelia dortmanna doesn't store much oxygen within its tissues. It is a plant of cold, extremely nutrient poor (oligotrophic) lakes meaning possibly that it doesn't need to store oxygen, because it is always available from the substrate. I couldn't find much specifically for Nelumbo, the plant with the <"spectacular aerenchyma">.

<"Environmental factors regulating the radial oxygen loss from roots of Myriophyllum spicatum and Potamogeton crispus"> is a paper about <"Root (radial) oxygen loss"> and it says that when the water column is oxygen depleted the plant leaks less oxygen. It doesn't really talk about photosynthesis or respiration.
...... During a sequence with a light/dark cycle as well as alternating aeration of the water column, maximum ROL with up to 35% oxygen saturation at the root surface occurred under light/O2-saturated conditions. A decrease to about 30% was observed under dark/O2-saturated conditions, no ROL was detected at dark/O2-depleted conditions and only a weak ROL with 5–10% oxygen saturation at the root surface was measured under light but O2-depleted water column. These results indicate, that during darkness, ROL is supplied by oxygen from the water column and even during illumination and active photosynthesis production, ROL is modified by the oxygen content in the water column.........
In our aquariums we aren't going to have those large differences in oxygen conc. between plant and water, and when we have "pearling" at the end of the photo-period we know that both the internal tissue of the plant and the water column are fully saturated with dissolved oxygen. In some circumstances the water may become <"super-saturated with dissolved oxygen">.

What we don't know is the rate at which that oxygen is used in respiration or diffuses from the plant leaf back into the water column. I will see what I can find for Myriophyllum, Cyperus, Typha or Phragmites in <"Constructed Wetlands">.

cheers Darrel
 
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Hi all,
I won't add to the last post, but this is an / the? <"Egeria densa"> paper:

Białowiec A, Sobieraj K, Pilarski G & Manczarski P. (2019) "The Oxygen Transfer Capacity of Submerged Plant Elodea densa in Wastewater Constructed Wetlands". Water. 11(3):575. says:
...... During the following days of the experiment, stabilization of processes and gas relations in the vessel with E. densa became visible. There was also a clear supersaturation of water with oxygen, which could be associated with a low BOD index. The amount of O2 remaining in the tissues of E. densa and in the surrounding water allowed not only to satisfy the plant’s demand for this element but also to release it outside. ......
Egeria_oxygen.jpg

cheers Darrel
 
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I'm pleased to see the topic has attracted your attention.
In our aquariums we aren't going to have those large differences in oxygen conc. between plant and water, and when we have "pearling" at the end of the photo-period we know that both the internal tissue of the plant and the water column are fully saturated with dissolved oxygen. In some circumstances the water may become <"super-saturated with dissolved oxygen">.
I'm not that sure about that. There's a functional link between the level of photosynthesis and the level of respiration. If plants create more photosyntates, they spend more energy on using them, i.e. respire. I suspect that diurnal peaks in oxygen satiation may be particularly pronounced in densely planted hi-tech tanks. (Unfortunately, there's lack of empirical data on my side, because optical DO meters are too expensive for my budget.)
 
Hi all,
For us dummies, running an air pump over night is only ever going to be a good thing?
Yes I think so. I'm keen on keeping the water column oxygenated, I don't think it really matters <"how you get there">. I'm a low tech aquarium keeper so I don't have any experience of high tech.

cheers Darrel
 
Hi all,
There's a functional link between the level of photosynthesis and the level of respiration. If plants create more photosyntates, they spend more energy on using them, i.e. respire.
That is true, but the differential between CO2 uptake and oxygen evolution is <"larger for more productive systems">. Because we know that <"one molecule of oxygen (O2) is evolved for every molecule of CO2 incorporated"> plant growth is a measure of the difference between CO2 and O2 use.
Unfortunately, there's lack of empirical data on my side, because optical DO meters are too expensive for my budget.
You can use <"pH as a proxy for oxygen level">.

cheers Darrel
 
Seen a few people that run an air pump with a diffuser in the tank to add Oxygen in throughout the night when the lights are off
From personal observation of my tank:
I run CO2 and associated pumps prior to light on and the lights stay on for about an hour after CO2 is switched of. This gives me a slot to feed the fish and look and the tank without the plants waving about.
Early morning observations in the gloom showed fish hang under the surface and not looking happy.
Added a smaller pump and timer (economy seven - basically overnight) and active fish observed in the morning gloom.
So for me removing CO2 overnight build up was a requirement.
Hope this is of some help.
 
As an aide, I've always wondered what the role is of the air in a sponge filter? Do the bacteria on the sponge require it? Sometimes I have to switch my pump off at night as I'm sleeping in the living room due to a mould problem. It made me curious about the role of air. I have 2 sponge filters in a 106L, along with a Fluvial 304, so they aren't "necessary" and I primarily see them as adding bubbles to break the surface. I have bracing on my tank so sometimes the water level is a little above the spray bar, and that makes minimal surface disturbance – sometimes I also direct the spray bar straight up and that does create disturbance. Don't mean to take us down a side road, but the question interests me and seems oxygen related. I like the simplicity of sponge filters as an addition to cannisters.
 
As an aide, I've always wondered what the role is of the air in a sponge filter?

If you mean an air powered sponge filter, the purpose of the upward flow of bubbles through the central tube is to force water through the sponge. The upward movement of the bubbles forces water up along with them, causing fresh water to be drawn in from the outside of the sponge. They simply wouldn't do anything without the air bubbles.
 
Hi all,
If you mean an air powered sponge filter, the purpose of the upward flow of bubbles through the central tube is to force water through the sponge. The upward movement of the bubbles forces water up along with them, causing fresh water to be drawn in from the outside of the sponge. They simply wouldn't do anything without the air bubbles.
That one. Have a look a the <"Czech style air lift">to show just how effective this can be.



I've always wondered what the role is of the air in a sponge filter? Do the bacteria on the sponge require it?
They do, the air provides the oxygen for both "ordinary" decomposition and for nitrification. Nitrification, the conversion of ammonia (NH3) to nitrate (NO3-) is an <"oxygen intensive process">.

cheers Darrel
 
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