Oxygenation Of The Water.....

[Mr Melt]

Allright lads.

The reason I have brought this topic up is simply because I'm worried about my new tank (Juwel Rio 180). My new external filter (Eheim 2213 Classic) seems a bit crappy (the current is pathetically weak). This worries me because the water is simply moving; there is no actual agitation of the waters surface.

Which brings me to my point; what induces oxygenation in a fishtank? (particularly a large + well planted one)

I'm terrified that I'm starving my poor Congos of oxygen =/

PS - I should note that this applies only for bedtime (for me). For the rest of the day I have an airbubble curtain blasting at the back of the tank =P

 

[StandbySetting]

You'd know if you were starving them, they would be gasping, it occurs on the principle of diffusion, whereby a substance moves from an area of high concentration to low concentration until an equilibrium is reached. Oxygen is one of the components of air, so will diffuse into the water column at a rate relative to the surface area of the tank, and the difference in concentration.

 

[Mr Melt]

You'd know if you were starving them, they would be gasping, it occurs on the principle of diffusion, whereby a substance moves from an area of high concentration to low concentration until an equilibrium is reached. Oxygen is one of the components of air, so will diffuse into the water column at a rate relative to the surface area of the tank.

In layman terms; the faster the current the higher the rate of oxygenation?

 

[StandbySetting]

Not necessarily, the higher the surface area, the higher the rate of diffusion, water with a larger surface area has the potential to 'hold' more oxygen due to the higher pressure being exerted on the body of water, the surface area can be increased by adjusting your filter outlet so that it causes ripples on the surface, but you shouldn't incur any problems by having minimal surface agitation anyway.

 

[Mr Melt]

Not necessarily, the higher the surface area, the higher the rate of diffusion, water with a larger surface area has the potential to 'hold' more oxygen due to the higher pressure being exerted on the body of water, the surface area can be increased by adjusting your filter outlet so that it causes ripples on the surface, but you shouldn't incur any problems by having minimal surface agitation anyway.

So then, as long as the water has a current (no matter how weak) then there is sufficient oxygenation?

 

[StandbySetting]

Current is irrelevant, water can have a high current but minimal surface agitation, if you want the highest levels of dissolved oxygen possible then it's all about increasing the surface agitation which ultimately increases surface area.

 

[Mr Melt]

Ah, so the more surface agitation the more oxygenation.\

2mrro I think I'll attach the other pipehead for the filter outlet; see how that pans out...

 

[Smells a bit fishy]

The more surface of water exposed to air= more oxygen in the water.

If say a tank is 2 metres in length and 1 metre depth. It will have more oxygen then one of 1 metre in length and 2 metres in depth as there is more surface area (touching the air).

It doesn't matter if there is current or not. Agitation just increases the surface area of the water.

I think that is correct. Please correct me if I am wrong

 

[eaglesaquarium]

You are correct. (although technically, you would want to mention that there was a third dimension (the width) that remains constant in your comparison for it to truly work.


Like this:

L: 2m
W: 1m
D: 1m

has a surface area of 2 square meters.

L: 1m
W: 1m
D: 2m

has a surface area of 1 square meter.

The first has more surface area, and therefore can exchange oxygen from the air more easily - all other things being equal. By adding waves, you can effectively almost double the actual surface area - amount of water surface actually "touching" the air.

 

[Tolak]

I always though friction between water & air came into play with this as well. With a more stagnant tank you will have less evaporation, which means less transfer of water to air, as well as air to water. A tank with more surface motion has a higher evaporation rate.

When you mop a floor & run a fan on it (common occurrence in my fishroom!) that water on the floor is not moving as far as I know, but you are increasing the friction between the moving air & the water. The floor dries faster with the fan, evaporation is increased.

Feel free to correct me on this one, it's been quite a while since I referenced this.

 

[StandbySetting]

That would be correct, fans create areas of differing pressure hence the increased evaporation rates

 

[Marto666]

Would an air pump make much difference oxygenating the water given the ammount of surface area of air bubbles exposure to the water?

 

[StandbySetting]

Not really, their surface area and contact time is minimal compared to that of the surface of the water on the tank, the ripples they produce however will yield a higher concentration of Air in the water column.

 

[eaglesaquarium]

Fans also move the saturated air away from the water at a much faster rate than would happen normally, putting "drier" air in contact with the water, increasing the rate of evaporation as well.

 

[Tizer]

To be quite honest, your rio 180 shouldnt suffer any oxygenation problems its usually only a problem with small tanks and breeding tanks, which can be overcome with air pump filters agitating the surface.

biOrb tanks for example are a good example, especially the rounded ones which hav a very small surface area when full up, or the fluval edge with a very small square gap. In which case people usually advise you to stop filling it up an inch below the top glass.