Use a damp rag and sprinkle a large amount of salt on the rag. Scrub the tank with that. That will clean all the Algae and stuff off the tank. Rinse the tank real well and wipe it out. The salt will hurt nothing as I keep salt in my tank at all times anyway at the rate of 1 tablespoon per 5 gallons.
Salt is safe for all fish.
I have no Salt Water Tanks. Now for a couple of other things. Heat, high heat kills anything. You could fill your tank after washing it with water, turn on your heater and heat it to about 95-100 degrees for a couple of days. This should not hurt your seals at all.