decor can have a huge affect on the success and health of the fish. my jaguar cichlid greatly appreciates his 6" PVC pipe T-connector. now oscars may not have terracotta pots in the wild, but they do have closed in places to defend as their territory, something you can simulate with rockwork, driftwood, clay pots, or PVC piping. an animal used to having a shelter/territory being stuck in a habitat (your tank) without that shelter could be stressed and obviously you dont want that. so give it something to hide behind and defend. oscars are from slightly softer and acidic waters, so that should be the goal, but blackwater extract would not be the best way to do it.