I don't know about the pecan trees but I definitely wouldn't use pine as it can contain toxins. Any type of oak should do, just take like 6-10 dried leaves and throw them in a pot of boiling water for about 30 minutes. Be aware, you might want a fan on when doing so as it can get quite earthy/leafy smelling (it doesn't bother me though). Then strain out the leaves and you'll be left with a nice pot of tea colored water.I have pecan trees and a few oak and pine trees in my area? your saying these will work? then i just boil them and add to the tank?