I have a 75 gallon tank with a picasso trigger, a hippo tang, an orange-shoulder tang, a percula clown and I added a koran angel to the system a little over the month now. This fish has fit perfectly into the system and has never really had any problems with the other fish. They seem to instinctively leave the Koran alone. In the beginning I thought water quality would be a problem because of the messy eating habits of the trigger, but they get along fine and my only filtration is a fluval 303 and a pair of protein skimmers. I love the fish's colors and he's one of my best eaters. Eat's almost anything whether it be brine shrimp, seaweed selects, nori, or just plain old flakes. I would be careful about adding the Koran in with the Singapore because angels don't generally get along well. But my father keeps a Maculousus and a Singapore together in a 75 and my uncle has an emperor, a singapore, and a koran all together in a 150 gallon tank. I was also told not to mix large angels and dwarf angles but the koran did fine w/ my Coral Beuaty. It seems that we have similar systems so in my opinion I would say go for it. If you do decide to get one, let me know how everything goes.