Bicolor dottyback or any dottyback is going to be very aggressive. Usually more aggressive than online stores will list them. A similar look alike is the royal gramma. They are for the most part peaceful, but like low lighting so they hide more.
Flame Angel is semi-aggressive so you'll want to add that fish last or close to last. If you're planning on having corals it's a gamble because some like to eat corals and some will never touch them. Some reefers say at one point an angel will most likely nip at coral.
A midas blenny is awesome. They have great color and they're such a character! Love mine and they have a nice movement like an eel. However, the engineer goby looks most like an eel when an adult. Their juvenile horizontal stripes will change to be vertical when they grow up. They get to be a foot long and will dig tunnels and move sand a lot and can eat small fish or inverts when large.
-30+ nassarius snails in a 70 gallon. More wouldn't hurt. Left over food (best CUC member IMO
-Serpent sea star (more peaceful than the brittle stars and is a great CUC member as well)
-some crabs (I've read blue legs are more peaceful than red legs so I just keep blue) Algae & left over food
-ceriths and dwarf ceriths (don't do much, but they help a little) Algae
- cleaner and fire shrimp (get left over food)
-turbo snails (clean algae quick, but can starve when it runs out)
I don't rely on the CUC for anything, but they really do help with getting rid of waste and eating scraps. Great for when a fish dies and is hiding so you can't get to it...they'll eat it before it adds nitrates.