For a 55, you will probably be safe with 2 powerheads. Just purchase ones for 55 gallon aquariums, or alittle more if they don't sell that. With bubblers and salt creep, my aanswer is no! bubbles stink. THey're loud, they cause devastating sat creep, and they are not necessary at all. With a skimmer or powerhead, you will be fine.
