"lee" writes:

I have access to large quantities of netting used for protecting garden
fruit.

How fortunate!

Its made from nylon like fishing line. Could this be used as a media
in a 55 gallon drum biofilter, and if so should it be cut up small and
placed in bags, or could I just pack it into the filter in one length.

It's what I use now. I just jam it into 32 gal trash cans. To clean I
agitate it a little and then drain the container. I have two containers
in series and have only needed to clean the first, I consider the first
the mechanical filter and the second the bio filter. Its the best media I've
found, goes longest between cleanings and easiest to clean.

I still want to try injecting compressed air at the bottom to loosen
debris and then drain. Hands dry, could even be automated...

Good luck.