When I lived in Ft. Lauderdale about 30 years ago, I would take my 20 or so empty milk jugs and go down to the beach and fill them up. I never had any problems and saved a lot of money. I even used beach sand in my tanks too. I would just let the jugs of sea water sit in the dark for a few days...
Mine eats flaked food, frozen brine shrimp, chopped fish and shrimp. He scrambles out of his hiding place and grabs what he can. I target feed him too, takes food right out of my hand. Pretty cool critter.