Use Easy Off Oven cleaner to clean fiberglass shower floor. Easy Off in the blue can cold method oven cleaner!!! Works perfectly! EZ Off fume free shower cleaner. Spray on floor, let sit 30 min to 1 hour scrub with stiff pad or brush (use gloves) and rinse well with hot water.
Heat 1/2 C White Vinegar in microwave for 90 sec. Pour into spray bottle. Add 1/2 C BLUE Dawn Dish Soap. Shake gently to mix. Spray on surface and let sit 1-2 hours. Just wipe it away and then rinse with water.