i keep my daylights on for 8 hours, and the actinics on for another 4, for a grand total of 12 hours daylight. naturally, we are trying our best to mimic the normal day at the reef.
life glo? marine glo? depending on what type of coral you plan to keep, and where it was originally harvested from, will dictate what color temperature your lamps should be. if you choose deep water corals, then a higher color temperature is optimum(between 14 and 20k). lumens are not the only thing to consider when choosing lamps for a reef tank. there is also PAR(photosynthetically active radiation)to consider.
i'm not sure that your 48 watt fixture will be enough for the more light demanding corals.
if you are utilizing a protein skimmer, and a decent amount of live rock, and keep your bio-load reasonable, you won't need any other types of filtration. the cannister has been known to be a source of nitrate, mainly because people maintain them as they did for freshwater tanks, and clean them too infrequently. if you decide to use the cannister, i'd suggest cleaning it weekly.
a protein skimmer for a small tank like that is going to be a difficult task. i'd suggest maybe the tunze nano skimmer. most of the smaller skimmers are junk IME. some might suggest the aqua-c remora, but i was very disappointed in the one i had.
you can get away without a skimmer with a strict waterchange schedule(i'd go with weelky 20% changes). that's probably the route i'd take with a tank of that size.
yes, more than 1 powerhead would be a good idea. the object is to create random flow. not just a constant blast of water. choose the gph
of your powerheads by learning the requirements of the corals you plan to keep.
you can utilize some freshwater foods. i'd suggest using them sparingly, and feeding the tank with a cleaner food source like some fresh foods. i tossed a bunch of stuff in the blender like clams, scallops, shrimp, and a few other things i bought at the local supermarket, then froze the puree flat in a plastic ziplock and feed that mostly. the tank is healthier for it. again, research the requirements of the creatures you plan to keep for a proper diet.
i wouldn't add any snails, hermits, or any other living creatures until the tank has completely cycled. the lights don't need to be on at all for the cycling process.
i'd add your snails and things as needed. the hermits are carnivorous predators and will eat anything, including your snails. sometimes they will kill them just for their shells. sometimes they will kill them for the heck of it.