I'm not sure what a small "scotter" is but I'm asuming that is a scooter, the only prolem with them is that you will need plenty of live pods in the tank for them to eat as just like the mandarins they "usually" only eat live food, so if your live rock is well established and can support one, it would be a great addition. Might I suggest a bi-color pseudochromis they can be a little tempermental sometimes but with only a few fish, and they being clowns should do really well. They are the coolest swimmers and I love how it looks like someone took two different color fishes, chopped them in half and then glued the opposite colors back together.