There's all kinds of growing medium - Perlite, expanded clay pellets, rock wool, and coco coire are probably the most popular. Pretty much any inert substance you can think of can be used to grow stuff in a hydroponic system. There are advantages and disadvantages to all of them, but almost none of them are both Cheap and Available at the grocery store.
I got this pool noodle for $0.95
@frickhaditcoming And this is not for starting seeds. You have to sprout seeds using some other method and transfer them to the pool noodles.
Sunbeam City is a anticapitalist, antifascist solarpunk instance that is run collectively.