Duncans are hardy little things. Mine did OK...but then I found a sweet spot for them with my flow and they ahve gone nuts. Looking at your tank, there isn't anyway it will get the flow it needs there. It looks like it is in a dead spot. Move it to the other side so the PH's flow can let its tentacles sway in the water. Yes, it has only been 6 hours and it needs time to adjust to your tank. But where it is isn't going to help it out any.