You are right in your identification, it's a Dragon Goby which is a brackish fish so it will require different water parameters than an oscar. There will also be a significant size difference between the two and the oscar would most likely harass the dragon goby to death. Tim is correct on the slow growth rate. I had one and in over a year it grew from a little over 6" to a little under 8", then I moved and it didn't survive the trip.