I usually just wash bog wood then add but I've never add a pice this size before just smaller ones which leach tannins but not as much I must admit though I do like the look.
The first Oscars that I ever saw were over 10 inch long and in tanning stand water at first I thought that they were fake not real fish as I'd never seen them before and when I realised that they were real fish I fell in love with them and that is what made me get some if I had not seen them I would of never gotten any Oscars at all. I'm going back over 20 years ago when I saw them.
And yes fish herder I got red bush tea for my dwarf cichlid as you recommended and she doing much better I'm giving it a few more days then adding male back in to tank and the tanning look really nice in tank it only slightly tanned though.