"Gill Passman" gillspamattaylorpassmanspam.co.uk wrote in message
.. .


I've witnessed the noise from those with external pumps and these
were not
for me...



Agreed. At my max of 10 tanks, I looked into an external, central air
pump. The noise, coupled with the air lines all over the place
convinced me to simply buy smaller pumps. Rena pumps are fairly
inexpensive, very quiet, and reliable, too.