Subscribed. I am curious as well. Especially cheap/free shipping.
May sound obvious, but check your local areas around Craiglist
I do it two ways. Using tags in "free stuff" and then tags in "all for sale"
I personally use a ton to make sure I find everything available and also check daily.
Examples, try
Aquarium, fish, cichlid, livebearer, tetra, platy, marine, API (depending on what you're looking for)