Some peaceful blues you might look at are, blue neon gobies, chalk bass, and, blue gudgeon gobies. With your fish, on second thought, I'd not go with the chalk bass because although they are non aggressive, they are likely to out compete your scooters, and, wrasses at chow time. neons and gudgeons should go well and they do well in groups, too. These won't help with the hair algae, though. Might try more snails and urchins for that.