I have a 5-6" delhezi and a ~5" ornate. Both seem to be retaining their external gills. There are only traces, barely visible on the delhezi, but they are there. On the ornate they are still slightly larger than on the delhezi. Both seem to have not lost any of their external gills since I got them (pencil thick for the ornate, medium thick 3" for the delhezi). Any reasons why?