I have found that the Multibar, Venustus and Regals are all fish that you have to have a really well established and mature aquarium.
I only get the Red Sea or Yellow Belly Regals. I currently have a pair of Yellow Belly Misbar Regals that came from Vincent at Bali Aquarium 3+ Years ago. Before a power outage in July of 2017 I have a Yellow Belly Regal for 5+ years. In that 5 years I would guess I only saw that fish eat maybe 5-6 times. It didn't care about any food in the tank. And it didn't seem to do that much eating during the day hours.
The regals are usually very shy fish. After losing the fish because of the Power Outage in 2017 I had a pair of regals in my outdoor tank that I moved inside. These 2 were used to being in a frag tank which didn't really have any hiding spaces. They are much more active in the main display tank and both are more interested in food.
Prior to the July 17 issue I also had a pair of Multibars for 5+ years. These fish are also a fish that didn't care about what food went into the tank. They just wanted to hunt the rocks. Even with fresh live brine, or black worms in the tank they would swim past.
After losing that pair, I did not replace them. I like the multi-bar. To me they are the poor man's Peppermint. But the Multi-bar would out of the blue decide to eat a bunch of Acans. I would put a couple of frags in. they would do well. I would put in some more and then after 6-8 months of the acan doing great in 2 days they eat them all. I do plan to get Multi-bar's again when i have a dedicated tank for them which is smaller where i can enjoy them (actually hoping one day to put a small tank for when sitting on the toilet in front of me for Multi-bars and clowns.
Venustus is a fish that challenged me or decades. But then I stared getting 3 or 4 at a time and had much better results. I currently have a trio of Venustus. 1 of them is 7+ years the others are 1.5 years. The Venustus is also a shy angel. It was months and months of sitting in front of the tank trying to see do I still have 2 or 3 or none. Because they just don't like to be in open water. Once the Venustus settle in they are more active than the other angels I've listed. But still sometimes it may be 2 or 3 days till I see all 3 at once to know they are doing well.
I have not had luck keeping the Colini. If I get them past a month, which is seldom then they just fall over dead at month 4 to 6. I don't know what I am missing.
And the other fish to add to this category is the Centropyge Aurentia or Golden Angel. I love these little fish. I was present when the first one arrived in the states. But this fish is so damn shy. After a tank crash 7 years ago I thought I lost my pair of Aurentia. It wasn't until 18 months after the crash that when editing some coral photos the damn golden photo bombed a pic. And a few months after that it turned out both Goldens were alive. And then 4 years after that while Vincent Chalais of Bali Aquarium was visiting, the darn things spawned in front of him (there is an article in a French Reefing Magazine about this event) unfortunately the article was published in July of 2017 just a few weeks after the power failure.
The success in keeping the angels you mentioned (in my opinion and experience) is to NOT Quarantine them. Most of these fish come from Regions where they had to have been hand caught (excluding Venustus).
These fish need to be able to go into a new environment and be able to hide in the dark and be comfortable eating on their own from things naturally available. They don't want to eat flakes, or frozen or pellets. They need to be hunting and gathering. Once they are comfortable that they can survive in their new tank then they MIGHT start looking at all the food we offer them.
With the exception of the Regals all the other angels also have to have a ton on rock/caves for hiding spaces. PVC pipe pieces doesn't work. When they are hiding in the pipes they are hiding. When they are hiding in caves of natural rock they are constantly picking at pods and food in the cave.
I have had good luck in acclimating these angels in my outdoor frag tank, because for some strange reason frag racks and frag plugs are a plethora of pods that make for easy feeding for finicky fish. I am amazed that a 8'x4' frag tank with just racks of frags produces enough food to support 8-10 angels (including adult imperator, navarchus and regal) along with pairs of Mandarins and Dragon Pipe fish. And even after them all eating pods all day long you pick up any frag in the tank and its covered in pods.
Dave B