allright, here we go, I Might repeat some stuff that parker has already said.
I would say no for now on the mandarin, wait for a while on it, at least a year or so, during that year you would impliment a as large of a refugium as you could, this would create a natural food source that woul always have new copepods and amphipods being reared. This would be for a mandarin that wouldn't eat prepared foods (most of the mandarins that are available) but if you find one that eats prepared foods your battle is halfway over. The problem with Mandarins in general is that they are constantly eating, so multiple feedings during the course of a day is usually recquired, though if you have enough copepods/amphipods in the tank and just suppliment with prepared food you could get away with less feedings. The firefish are AWESOME FISH!!! Make sure to get a pair, do not buy them seperately, but buy two that have already paired up, have the store bag them together, and introduce them to your tank at the same time, and in time after they have gotten over their shyness they will soon come out and be beautiful centerpieces to your tank, however these will eat copepods and amphipods as well, but not in the large amounts that the mandarin will. As far as a flame angel, these are known to nip and eat some corals and inverts (like clams!), some will not show any signs of being pests, and then one day they can just start in on nipping on stuff with a vengeance! SO, basically beware, some people never have problems. If you do decide to get one, make sure you get one that is collected in either Hawaii or Australia, they don't use harmful chemicals to collect angels, unlike other places. I would go ahead and forget the damsels, they are natorious for being territorial, and many people end up trying to catch them to no avail, and have to resort to literally fishing them out with a hook and line. Damsels eventually lose their beautiful colors and start turing darker and duller. Chromis are one of the only damselfish that I would even think to put in a tank other than a percula clown (yes clownfish are damselfish, many people don't know this) If you get about 3 chromis they will school and it is really cool, but they do eventually lose their vibrant colors. Percula clownfish will also become territorial as well, but if you introduce a small one after some of the other more timid inhabitants, you should be just fine. The lion fish would do well in a species only tank, sorry. I believe that Royal Grammas can be very territorial as well, but this is one fish that I have never kept, so I can not honestly tell you yes or no, wait for someone else to post on it or do a search on liveaquaria.com or something of the sort to see what they recommend.
Corals do add a really nice element to the tank!
