Aireation in a tank

[Becca]

Ok, I have a question.

I've heard that you don't need an air pump / air stone if you have a filter that moves the surface, but I've never heard why. Can someone explain to me how moving the surface of the water helps to incorporate aeriation into a tank?

Also, how do you know that you've got enough surface movement from your filter to nix the airstone?

 

[cutechic]

By moving the surface of the water, it allowes more gas exchange to take place, which means that more oxygen can get into the tank, and CO2 will be released.

An airstone does not add oxygen to the water, but creates movement which also helps gas exchange take place.

IMO, airstones are unnecessary if the filter creates enough surface movement, but that's just me.

 

[BigSteve]

♂ Easy. When the surface of the water is agitated, some oxygen is
"exchanged" from the air above water surface, and some oxygen is introduced
into water. You don't need (or want) tremendous surface movement do do this.
How do you know if you have enough? Hard to say. But a filter like a hang-on-
back Aquaclear, Penguin Bio-Wheel, etc., is going to provide more surface movement
than an airstone. The bubbles of an airstone look cool, but they are not really providing
oxygen... it's when the bubbles get to the surface and agitate it that the oxygen is
exchanged. If in doubt, add an airstone, but those typical green ones made of a sort of
bonded sand/silica material break down, introduce silicates into tank, and can increase
algae. I've never seen or heard this discussed anywhere, but it's a theory of mine from experience and observation. If you get an airstone, get one of the wooden ones, or some other medium besides the bonded sand type.

 

[bobbobbob]

The bubbles of an airstone look cool, but they are not really providing
oxygen... it's when the bubbles get to the surface and agitate it that the oxygen is
exchanged.

I thought that the air in the bubbles produced exchange too - afterall the surface area of the air overall (bubbles plus surface) is increased and that is what you are doing by rippling the surface of the water in the tank with the filter.

In theory, you should be able to despense with airstones and filters if you have enough plant in your tank (trouble is, you can't see the fish!!!)

 

[Teelie]

I use bubble wands as they're often called to make a current, for their appearence and to help agitate the surface of the water though this is mostly an irrelevant one as I have two HOB filters that do plenty of disturbance, especially when the water level runs low.

 

[CFC]

It is a common myth that aquariums need a stream of bubbles to keep the inhabitants alive. In the days before power filters airstones were used to provide movent within the water column circulating the water around the tank to prevent the water at the bottom from becoming stale, they also provided the much needed surface aggitation that allows gas exchanges to take place. Now days all the water circulation and surface aggititation is done by power filters which circulate the water at a rate of hundreds of gallons per hour compared to the old air powered sponge and undergravel filters which has done away with the need for a airstone other than for cosmetic reasons.