For that size tank an AquaC Remora or a CPR Bak Pak 2 will work well. Other filtration can be all natural with LR
. You can supliment with mechanical/chemical filtration but its not needed IMO
. I would suggest using 1 power head with a wave unit like a SCWD. Adding other PH for flow if needed depending on the coral your going to use.
Lighting is something you didnt mention, what do you plan on using?
I would go with a sand substrate.
You can stock clowns, basslets, wrasses, chromis, as well as many more. You can try a dwarf angel if you wish.