Air stones for UG Filter

[Sadielynne]

Do you have use airstones in the lift tubes of undergravel filters or can you go without, just using the rigid tubing?

[Diana]

I would use a coarse airstone.
The more bubbles the better.
Larger bubbles are not more efficient.

You are trying to fill the up tube with a constant mass of rising air across the full diameter of the tube. This is lifting the water and creating the current.

A few large bubbles will not move the water so efficiently. If you watch large bubbles, you might see that one follows the others, like race cars 'slipstreaming' or 'drafting'. They are not each and every bubble moving as much water as possible. Instead they are finding the easiest path to the surface by following where another bubble has already disturbed the water, gotten it out of the way. You do not want the water 'gotten out of the way'. You want the water to stay with the air, and rise.

I say a coarse bubbler, because your pump might have to work too hard to force air through the fine mist sort of bubbler, and with less total air moving then you are also losing the lift.

[driverellis]

Thanks for the nice sharing,i have never know about it.