i disagree.
i had an airpump that i received free with a tank from freecycle, it was attached to a long airstone.
i have managed to transfer most of my fry into a small tank away from the hungry females, but i have recently moved house and couldn't find my sponge filter, i'm totally broke at the moment, not even got £10 to spend and needed something really delicate for my babies to cope with, power filter no use here!
i made a mini one of these last night, the babies seem fine with it, some of them have even decided that squeezing down in next to the filter floss is a cosy bed!