Bay tank to saltwater

[Foliveira323]

I have 4 tanks right now and am looking into getting into saltwater. I have a bay tank right now that is between 17-19 ppm. Is there an easy way to convert or should I start from scratch????????

I have a 30 gallon with heater, power head , filter for up to 50 gallons and lights... I have local bay rocks and some shrimp and crabs from the bay in the tank.. I have bay sand as a substrate...

I know that I need to upgrade the lighting.. But wondering what else I need to upgrade and what I might need to eliminate???