As far as skimmers are concerned, i dont think they are definitely necessary for a 55 gal reef. Often people choose to put a little skimmer in such a small tank which ends up not working very well or not working at all. I my first tank was a 55 FOWLR and i then converted it to a reef. I never needed a skimmer for mine. They key is to reach a really robust balance of all different types of creatures in the tank. (aka time to become an esablished tank). I had a 48" power compact light fixture with 4 24" 96 watt bulbs, two blue and two white. Always always get a ton of light or dont bother buying corals because they will not thrive and will probably die or look like crap. Metal halide bulbs are the best for sure but they get too hot for a small tank for a 55 gallon tank and you'd cook your fish. The blue lights would come on 30 mins before the white lights and stay on 30 mins longer at night to simulate dawn and dusk. The only protein skimmers that actually works amazingly is the ASM line and I would recommend the ASM G2 skimmer. This an expensive and big skimmer for your tank but trust me- other skimmers will be an eternal headache for your tank. Also Tunze is a german company that makes exceptional skimmers that are very small, but they are very expensive. Like I said, I never had a skimmer and I was able to see great coral growth (due to the amount of light). Also, it is very very important not to have too many fish. It is so tempting to have a little tank with all these corals and a ton of beautiful fish too, but you really need to pick a very small number of little fish for the tank (less is more). For example, a longnose hawkfish, a zebra damsel, perhaps a yellow tang and a mated pair of percula clowns would be a really cool looking setup and probably the absolute maximum amount of livestock possible. I always add a ton of the smallest hermits I can find because they clean up so well and never do any damage. This way you never have to worry about overfeeding your fish because there will always be scavengers to clean up. Finally, a sand sifting starfish is certainly necessary- you rarely see them but they really keep your sand clean.
