The majority of wood in my tanks is wood i have found. I just ensure it has fully dried out and is hardwood (majority is gum tree). I have 15 tanks and buying wood for them would be far too expensive.

I dont take from rivers at all or from where crops are grown. I take from near livestock paddocks. I have been using it for many years with no ill effects

This was one set up...shows the wood layout...and the other pic shows it planted

Manzanita branches are commonly used for planted tanks i see. You may want to look into that.