is that picture of the 150g in your set-up? it doesnt look that large, and your oscars should definitely be WAY bigger than 4in at a year old, but if that is indeed a 150 then you could add a EBJD however i would try and add a larger one since they tend to be slower growers and oscars are fast growers, at 4in they wouldnt eat him but in a couple months time when they are double that and he has only grown a couple inches he could easily be food, there are some killer Os out there but for the most part as long as its not small enough to be considered food they usually leave it alone