Thank you Matteus for your nice comments. It's appreciated.
Most of the things I have added to my tanks over the years I have researched to see if they are suitable.
This information does not always come from fish, sites, forums or books.
In some instances I've had to research trees to learn about any possible toxins.
Collecting leaves is relatively risk free.
Most of the compounds held in leaves are released back to the tree before they finally drop from the branch.
As long as the leaves come from deciduous trees and are completely dead, then they will be ok.
The only real thing that makes some leaves better than others is longevity and how much tannin they hold.
I've not really ever had any problems with anything I have added. I steer clear of things that are known to carry toxins, but I do experiment little.
When I add something that I haven't used before and I'm a little unsure, I watch the fish like a hawk.
I've yet to have an issue. Tell tale signs that something was not agreeable would be faster gill movements and fish rising to the surface for air.
If you add anything and witness the fish acting like described. Take it straight out and do a large water change.
Collecting your own materials is a great way to fill a tank with natural looking decor. It's easy to come by, it's also free so your not limited in how much you throw in.
It would cost a small fortune to create some of my scapes with shop bought drift woods.