Oh man your going to spend some serious $$$, this is the main reason I stay freshwater. Breeding in a 55 gallon is surely doable but your going to need the fixings as mentioned. A good skimmer, lights, live rock, coral and tons of powerheads depending on the coral (but you probably dont want any ph's as your hoping for fry so types of coral you can get is going to be very limited).
You can keep your filters but your basically going to have to go through your whole cycle as fresh water and salt water bacteria are completely different. Lets put it this way, nothing and I mean nothing positive happens fast in salt water fish tanks. Your cycle is probably take about 2 months unless you got a buddy willing to give you some of his filter media.
I honestly think that salt is more work than its work but to each their own. And ps if your on city drains you can just throw your salt water from water changes down the drain, if your on septic dont do it.. your going to basically kill all the bacteria in your septic system and cause a stinky and very messy situation..
GOOD LUCK!
