I think Regal Aquarium (Bath Ave Aquarium) closed a year or so ago if that's the one you're referring to. You're not far from Pop Corals, 67th st/13th ave
there is a store on bay 16th and bath was there like three month ago they say that they will have salt water staff not sure if they have it now here #718-241-6688 this is other location they have you can call them if they have salt water staff
by the way Pop Corals are not to far nice store