Our seahorses and CBB did very well together. Both are very visual hunters who study their prey and then strike. There didn't seem to be any incompatibility nor competition over food between them. Mandarins went well in the mix too. For all three of these fish I think large populations of mini brittle stars helps lead to happy, fat fish. They grab the food and hold it in place but keep it wiggling perfect for this type of fish to spend time hunting and digesting long after you are done feeding the tank. Keep in mind the water quality impact of the heavy, frequent feedings that all of these guys require though.
For fish like CBBs , mandarins, and seahorses, it pays to watch their eyes while they hunt. If they are fully focused on their food, you are in good shape. If they are on a swivel keeping an eye on tankmates while they try to eat you need to reevaluate your mix or end up with a skinny, stressed fish.