What pump size to power 2 x 12" airstones.

[octofasciatus]

I need a air pump to power 2 12" airstone blocks. Would i be best using one pump and splitting the airtube between stones or using a pump for each airstone?
Please advise.

Many thanks in advance!!!

 

[scubasteve06]

I'd get a little more powerful pump than you would for just one and plumb it to a gang valve.