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Does adding O2 benefit the planted aquarium?

Anything that releases fragrance into the air will release it into the water too.

But that's besides the point. If your tank smells bad enough to require deodorant, something is wrong.....
 
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So the point is....good water agitation doesn't require an airstone...
 
Ive just read Darrels link. I must say I highly disagree with Clives point. He says that adding more o2 into the water doesnt really make fish withstand more co2. Well this is very easy to falsify. In most tanks with a wet and dry filter people are able to inject really high levels of co2. Why? Because there is more o2 dissolved in them. the relationship co2/o2 is very important. We cant say 30 ppm is the maximum fish can handle because this depends on the o2 levels between many more things.

now this doesnt mean there isnt a limit. It just means that at higher o2 levels fish can live well in higher co2 levels. The levels vary with each fish, health condition etc etc.
 
I think people are getting misled as O2 injection is often done in commercial fish farms. Done for one main reason, you can keep more fish per litre/cubic foot etc of water than without from typical air max of 0.5lb of fish per cuft to 0.75lb. Thus more fish to eat/sell for same tank.

Also done as tanks are generally small surface area wrt volume so won't absorb sufficient O2 from the air (air bubbling is only small O2 as bigger surface is better) and also O2 injection before filtration to improve filters.

O2 is expensive so is usually injected under pressure, best method is 20m deep hole with U tube in. You inject you O2 bubbly water down the tube were ar depth the hard to dissolve O2 dissolves. When is comes up is saturated ready to be diluted and given to fish. O2 is never bubbled in as expensive and in the short time is is in the water wont dissolve to make any difference.
 
I just look at it simply...
fish, plants and bacteria need o2 when the lights are off so, as long as it isnt a pain, lifting the outlets before bed cant be a bad thing. It also helps keep any surface scum at bay. Certainly in my experience increasing agitation at night help keep things tidy but that is most likely because the tank isnt perfectly balanced in the first place.... ill take anything that helps counter act my blunders.
 
I just realized thet maybe I took Cegs words out of context. So I stand corrected by myself since its not very clear.
 
ian_m said:
air bubbling is only small O2 as bigger surface is better
Click to expand...
It also improves circulation in tanks (especially in tanks with low circulation, (like in people's first tank with just a little LFS filter in it) and few plants), by circulating oxygen rich surfacewater with oxygen poor water from deeper layes.
 
All I know is the o2 goes on at night, if the fish have had too much co2 and they recover, but from what I can tell switching it off at a non photoperiod i.e midnight is a good thing as plants give off o2 when resting as all plants need to rest or they melt don't they?
Plus it saves a load of money if co2 is just being vented to air if no lights are on right?
I did have someone suggest to inject pure oxygen with the co2 not sure how the dissloved o2 would compete with the co2 at the same time and I mean not an airstone. but via a o2 diffuser!
 
Hi Jay1,
Jay1 said:
plants give off o2 when resting as all plants need to rest or they melt don't they?
Click to expand...
Nope, plants give off O2 when they're photosynthesising, not resting, when they are resting (ie. at night/dark) they require oxygen intake like the vast majority of life.
cheers phil
 
So maybe if Jaap agrees we could just say:
- how many of us add O2 at night?
- Do you see benefits?
- How is your surface ripple in the day?
- CO2 levels that you have (or think you have anyway)?

........I think this might help people decide?
 
Hi all,
Jose said:
So maybe if Jaap agrees we could just say:
- how many of us add O2 at night?
- Do you see benefits?
- How is your surface ripple in the day?
- CO2 levels that you have (or think you have anyway)?
Click to expand...
I think people need to be very clear whether they are talking about low or high tech.

Low tech.
In a low tech situation having a lot of flow and surface ripple increases the amount of CO2 in the water during the photoperiod, and decreases it during darkness when plants are respiring, but not photosynthesizing. The same principle applies to dissolved oxygen, during the photoperiod, when the water is fully saturated with oxygen, oxygen will out-gas to the atmosphere, and at night it will diffuse in.

In low tech. with a large gas exchange surface levels of all dissolved gases will more closely follow atmospheric gas levels (dependent upon the solubility of each gas and the proportion within the atmosphere). Gases are constantly being replenished and out-gassed at the gas exchange surface via the diffusion gradients between water and air.

A lot of people on other forums don't understand this, which is why people say that you can't "have much water turn over", or "run an air stone" etc., in a planted tank, and that "plants will kill fish at night by using up all the oxygen".

High tech.
The difference here is that we are adding CO2. Carbon dioxide is a very soluble gas, but water (at equilibrium with atmospheric gas levels) doesn't contain much CO2, because CO2 is a very minor constituent of the atmosphere (~400 ppm CO2).

When we add CO2 it will be lost at the gas exchange surface because there will be a steep diffusion gradient between atmospheric CO2 levels and the enhanced CO2 levels in the water. During the photosynthesis CO2 will often be the limiting nutrient, if we add more CO2 we can get higher levels of oxygen evolved, which we often see as "pearling" where the tank water is 100% saturated with dissolved oxygen.

As soon as you stop adding CO2 its level will begin to decline back towards equilibrium with atmospheric levels, how quickly this happens will depend upon the gas exchange surface. If you don't have much gas exchange, or a large bioload levels may remain elevated. Levels of dissolved oxygen will follow the same pattern, they will decline as the bioload utilizes the dissolved oxygen. How low they fall will depend upon the gas exchange surface and the bioload.

I'm not an added CO2 user, but if I was I would want to reduce CO2 levels as rapidly as possible outside of the photo-period. For me in any situation maintaining dissolved oxygen levels near to saturation is a win-win situation.

Problems for fish can occur where levels of CO2 remain elevated, but dissolved oxygen levels fall.

cheers Darrel
 
dw1305 said:
Problems for fish can occur where levels of CO2 remain elevated, but dissolved oxygen levels fall.
Click to expand...

Hi Darrel,
My understanding is that that is more likely to occur in tall narrow tanks with little surface agitation as O2 can't diffuse to lower levels easily; true? or part of the Matrix?
I do know when I went to reverse-flow under-gravel via a canister filter with no surface agitation my fish weren't happy, and I had to use a"Y" splitter to divert 1/2 the flow direct to the tank to give surface agitation.
cheers phil
 
Hi all,
Another Phil said:
My understanding is that that is more likely to occur in tall narrow tanks with little surface agitation as O2 can't diffuse to lower levels easily; true? or part of the Matrix?
Click to expand...
Definitely true, in fact I think <"tank surface area to volume ratio"> is one of the most important factors in aeration. I also think that it is one of the reasons for the success of <"Tom's original bucket">.

It was the problems of maintaining large rheophilic fish in relatively deep tanks that led me to write <"aeration and dissolved oxygen ....">.

cheers Darrel
 
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