airstone

[the Dregs]

Would a Millenium 3000 (double HOB filter) provide enough surface agitation for a 47T tank? My fish seem happy, but you guys got me worried.

 

[Rbishop]

Hi I am a reasonably new to the world of aquariums and am wondering a few things.
1. What is the benefit of an airstone.
Is it just for the asthetic or does it have another purpose.
I already have a good internal filtration system.
2. How many fish is too many?
My tank is only 23 ltrs I have 2 goldfish but was thinking of getting some snails of something like that.
I would also appreciate any tips or general info.
Thanks looking forward to some wisdom

They have many purposes..

Drive an UGF, though there are better ways to do it...
Drive a sponge filter...
Prevent stratification and dead spots..
Increase circulation...
Increase surface agitation..

Water, at a given temperature, can only be saturated to a given level with oxygen, unless the whole system is under pressure. Which is why when running high temps, like for speeding up the life cycle of ich, most folks will recommend adding an airstone.

Despite the generally accepted point of view, bubbles do exchange gases as they pass through the water. This gas exchange is all but instananeous as the saturation point is maintained based on ionic charge.

And, some fish just like to play in them, as well as many folks like their look.