Amazing things

Amazing things grow in my water garden called aquaponics.
A Neem tree appeared , without my help , recently.

I have two Neem trees in the backyard . One is doing ok but the other is more of a bush.
I noticed the ok one was blooming this year but I did not see any seed form.
Recently, however, I pulled an 8 inch tall Neem tree seedling out of the aquaponic system,
The  roots were amazingly about 18 inches long.

How did it get there ? Had to have been a bird bringing the seed from my ok tree to the planting medium
bin or to the net pot in the system.

An YES I am sure it was a Neem tree.
I sent it off to live in a neighbors yard. I will watch and see if it lives.