Aside from being up to the individual angel, feeding them heavily is a requirement, period. If your filtration and skimmer are not up to the task, or you travel for work etc., don't bother keeping an angel in a reef. While many people think they're feeding heavy, often times it pales in what these fish actually need. Tangs and Angels in the wild are plump.
All Angels will go nipping if bored or hungry. IMO, boredom can be somewhat curbed by giving enough random flow to almost move a 10 pound piece of liverock. I have what most would consider an (uncomfortable) tidal surge. The upper one foot of the tank is without coral, and fish venturing into this zone have a hard time swimming straight. My Achilles and Passer Angel often share the flow to the other end of the tank.
In a 6 foot 150 I have 4 Vortech MP40s on full blast with an Iwaki 30 return pump. This calculates to over 80 times turnover. When funds allow, I will add two more Vortechs, as the SPS will eventually cause flow rates to decrease. Trying to keep Angels in soft coral and LPS dominated tanks would be the ultimate of challenges and possibly playing with fire. My reef is 100% SPS dominated.
When first adding an Angel, many times they've been starved at the LFS or fed lightly in your QT for fear of pollution. My Passer immediately took to a Green Hydnophora for a quick nip within a minute of introduction. A rash decision would have been to pull the fish immediately. Since I average 4 cubes of frozen throughout the day, plus pellet and nori, I can't remember when he's last nipped at an SPS or clam. Because of this feeding regime, I have large sumps full of Chaeto and liverock with half the display's water volume in sump volume. I also have a downdraft skimmer sized for almost 3 times my tank, and perform a 50 gallon weekly water change religiously. Although I have 1 pound of live rock per gallon of tank water, only 120 pounds are in the display with the rest in the sump. This open space, especially at the top of the tank has been essential in providing an airiness that allows for more swimming room and less encounters between fish that may have a propensity to tear each other apart.
I also feel that small schooling fish like Anthias and Chromis act like little mosquitoes getting in the way of the big boys fighting. Bob Fenner calls them "ditherfish", and their darting in and out of corals and live rock caves is a wonderful distration for larger predators like passer angels.
I'm not naive in believing my 150 is the final home for these fish. I'm currently building a 500 gallon plywood tank in the garage, that will have a dedicated 300 gallon sump. So far, this method has worked for me very well. Angels will on occasion nip at your sps, but I really feel they're not interested in them as a meal as much as LPS and Softies. Keeping up the flow, feeding more and filtering heavily have been successful for me. A fellow reefer offered to take my passer off my hands for his aggressive fowlr should he turn on his tankmates and my sps. That was too long ago for me to remember. Hopefully DJ Reef doesn't think I'm a know it all. I'm not an expert by any means. All my SPS have been fragged and given to friendly reefers free of charge in the event that the Passer wakes up believing he's in an all you can eat buffet.
Any angel, in any reeftank, is a chance. I feel with the right specimen, and withthe right attention it can be done to an extent. Not for the faint of heart, but definitely some of the most beautiful fish in any tank if you're an adventurist soul.
Never touched the sps, without question the best fish I've ever had
