In "A practical guide to choosing your aquarium plants", Peter Hiscock
advocates letting one of the sponges in a canister filter clog up so as
to allow for anaerobic bacteria to develop there, as a complement to the
anaerobic bacteria which are (hopefully) building up in the substrate.
For the same reasons, he advocates a flow rate of half the typical
recommendation. He writes, "The ease with which water flows through
[medium/large-grade inert gravel] substrates will remove nutrients,
create oxygen-rich conditions, and cool plant roots, all of which will
severely hinder plant growth." Obviously, he is a strong advocate of
substrate heaters. Published in 2001 by Barron's. I think it's a solid
book. How do the above assertions sit with various folks' experiences?