Looking for Alders (Alnus sp.) in Melbourne's east

MadHatter

This is perhaps an unusual question for this forum, but I figure you guys are probably the best folks to ask...
I am trying to find a source of alder cones for use in my aquariums and would prefer to collect them myself. I just need to find a stand of alders to collect them from. I'm in the eastern suburbs of Melbourne, so would prefer to find something out this side of town. Naturally it would also need to be accessible from a public area - I would not want to enter private property without permission just to deprive someone's alder tree of it's cones.
In case you are wondering what use they are in an aquarium, they purportedly have antibacterial/antifungal properties and can thus can help prevent fish eggs from developing bacterial and fungal infections.
So, any leads would be gratefully received.
Thanks in advance.