wood.......

can i use wood from my backyard?

i would not use anything but driftwood. my friend put oak in h is tank and it jacked up his tank. it turned the water yellow. PH was jacked up too

well what makes driftwood .....driftwood? is there a type of tree that produces better driftwood than another?

drift wood is found underwater. really all it is is waterloged wood that is treated

If you boil it over a span of 3-4 days and change the water every time it gets yellow/brown you can release most of the tannins and help water log it.
You should only use hardwoods that are very dead without any green or sap and they should be brittle.
You could also run the same PH test on the wood that you would with rocks.
I have used citrus and cypress with no ill effects.

tannins, arent those heathly? only thing that makes them undesirable is the discoloring of water?

Yes and no it depends upon the fish. Tannins in large amounts will turn your PH towards the acidic side.
A small amount wont make much of a difference but you do want to bleed your wood some. Plus the boiling process helps speed up the waterlogging process. Heat makes air expand thus driving the excess out of the wood. Variations in temperature allow the water to seep in when the wood is cooling, heat it again and drive more air out.

danm fern you are pretty smart with fish

Thanks I try, I still have lots to learn though.