Ok i'm retyping what i bloody already wrote, as my stupid phone deleted my original reply!!
HUMPH!
Angels are great fish, but they often come with the arguable question and challenge of, are they reef safe? Well this comes down to a number of things and there are curtainly, in my opinion, ways to counter this behaviour. First thing to remember is each fish, like with most animals, is different, forget the species for a second - i'm talking each about fish has its on personality and therefore its own habbits and functions. What one might do, another may not! So some of it is down to luck in some respects. Some poeple own angels that have never touched a coral in their life, others have angels that snack on anything fleshy!
Secondly, species. Each species has its own natural innate behaviours, this can cause curtain species to be known as coral eaters, and others as reef safers!
So lets look at the third, final factor and most important!
why? Well Angels are wild creatures, and in general a species that has not yet been bred successfully in captivity. In the wild these Angel fish will eat by
grazing regulary all day to feed their hunger. Therefore Angels behaviour is innately programmed to nibble at food, and constantly eat. When placed in an aquarium the fish is suddenly made to eat once a day with no grazing foods. Makes for a confused Angel LOL! So they look else where to substain their appitites!
yep! your coral!!
So how can we try to stop this behaviour? Well i dont suggest letting algae overrun your tank in order to feed them! But what is beneficial to these fish (dwarf or regular) is a regular supply of dried seaweed clipped to the side of the tank! YUM!
Also some dried mouldable food that can be fixed to a rock to allow grazing on the rock all day. The angels diet consists of algae, sponge and meat. They should be offered both. A good food to provide them is oceans nutricion Angel Formula.
Angels should be housed in larger sided aquariums (yours is fine!) and provided with lots of live rock to hide behind as well as to pick from.
They are generally quite peaceful but can certainly hold their own against a tank bully. They appreciate space for swimming too. In general terms they require very good water quality.
So.. your choice! The
FLAME ANGEL! Well.. brilliant choice! Colourful, and robust and probably the most hardy of the dwarf angels! The Flame angel will fit nicely in your tank, and be a fantastic addition, they are not normally a big issue for coral nipping and take well to aquarium life (still offer seaweed and food you can mould on your rock!). Only downside - the price. I'm hoping your aware that this fish costs about £70 in the UK.
And your considering the
MULTIBAR ANGEL. Sorry to shoot you down here but a number of things concern me regarding this! First - major coral nibblers, this is one of the dwarfs that tend to snack regularly even with regular feedings! Second issue is that theres a 'only one dwarf angel per tank' rule, as they will often fight to death. I'd say leave this one out!
Tangs are next on my topic list! Beautiful and magnificant.. and evil!!
Tangs are great fish and in a tank your size you could house certain species. Tangs are best kept as individuals, and cross matching species should be kept at a minimium. Tangs are bullys. They like to be top dog and they're usually big enough to kick most fishes asses! They tend to not challenge bigger fish. They need lots of swimming space as they spend most of their time swimming! like Dorys says "just keep swimming, just keep swimming, swimming swimming!!"
So whats on your list!
YELLOW TANG - one of the best. BRIGHT YELLOW, what other fish can be so sunny and happy looking! NONE!
Would fit in your tank, remember he likes to swim! Yellow Tangs can be naughty with other fish and bullying, especially other Tangs with yellow on them! Eats mysis, and other meaty foods, also an algae grazer so will snack on that dried seaweed!! Tangs are grazers too! One of your last to add!
The
POWDER BLUE TANG or the Dory substitute as i like to think of them as! Again, great fish, needs swimming space and eats meaty foods such as mysis and brine. Would fit in your tank no problem, not known overly for bullying but as with most tangs, they can. Again one the last fish you add, i'd add before the yellow tang though.
Lastly
REGAL TANG hmm the issues is, they get MASSIVE and really they need a 6 foot tank as min and a lot of space to swim. I cant remember you specs, but i think it's a lil too small!
Pretty peaceful though, tends to follow other fish around and can annoy them. Very prone to white spot. If your specs fit add him whenever. The very small tend to die very quick!!
all tangs are prone to white spot. common mistake - its easy to deal with it. its a PAIN! You can treat in a hospital tank, but the main tank takes weeks for the parasites to die, and no fish can be allowed in during this time. Or get a cleaner wrasse or neon goby to control numbers.
wow this is taking forever!! lol
ROYAL GRAMMA - never had an issue with aggressiveness. They have their terroritory and will stand their ground to protect it but ultimately once terroritorys have been agreed, they mind their own. I wouldn't say it mattered when you add them but some would disagree. They eat meaty foods, and are very hardy. Completely reef safe. They live in the grooves of the live rock, and when scared they hide in their groove. They are brightly coloured but tend to just float near their hole, darting around occassionly at feeding. For the reason i think they're a bit boring i put them as amber. Your choice really! they are very nice colours though and completely appreciate why they are so popular!
ORCHID DOTTYBACK exactly the same as Royal Gramma, slightly different species. Most are more shy than the Royal. Same issues, as above, same benefits/care needs. YOU MUST ONLY KEEP ONE (dotty
or royal)
Chromis / Damsels - if you provide a ton of space then cool, but they are very very aggressive and will bully anything it can get away with, especially the clowns. Suited to your size tank no problem.
GREEN CHROMIS- i've only recently appreciated how cool these fish are, but only when shoalling! Aggressive by nature, but if kept in a group, they are aggressive only to each other. They should be kept in groups of 5 upwards and when purchased they should been in a tank together, swimming together. Do not buy independantly of each other as there are storys of them killing each other to become pack leader! They are harmless to inverts and corals, and eat meaty foods. Provide rock for them to hide in if scared.
DAMSEL CROSS very aggressive and go a horrible beige when adult. Would advise against it. Most damsels end up at being returned after a few months. They have a rep for biting hands that are put in 'their' tank. They eat meaty foods, and dont require much space. If an aquarium isnt over crowded then there is a chance this damsel could be kept agression free but its a HUGE risk as most are.
BANGAAII CARDINALS known to many as boring (**COUGH** SEFFIE!!!) but as put by fishy 55599 'elegant swimmers!' They bob all over the place, and have a wierd fasination with anemones!! They are meat eaters, and dont require much. They like good water quality and are very placid and peaceful.
They are funny to watch and although they dont move much, their presence is always known! Not a fish that hides thats fo sho! suited to your tank.
FLASHER WRASSE- wrasse, a beautiful fish but WITH CAUTION. 2 issues with wrasse. one, they jump, as in yes, they jump out the water and onto your floor where you discover them a week later when the smell kicks in!
two, they can eat urchins, shellfish and some other inverts (just watch out) Flashers, however tend to leave these alone with a good feeding routine. Should fit in your tank nicely and have no special requirements like other type of wrasse. They are very peaceful.
Ok, i'm out of time, sorry! will do the last 2 tomorrow!
Sorry this last bit was a bit rushed. Took me ages and i need to go out. Any q's then ask, i'll be back tomorrow to finish. Hope that helps!!
Brilliant 
I also read they need 100gplus, my tank is a little over this so wanted some 2nd advice 
