Tap Water Safe:Tap Water Safe removes chlorine and other halogens chloramine and heavy metals found in tap water which are toxic to fish. Tap Water Safe also contains a special protective coating that reduces stress that may be caused by transportation of newly introduced fish.Filter Starter;A live culture of \"friendly\" bacteria for your filter. These bacteria breakdown fish waste and prevent the build up of toxic ammonia and nitrite. Add to the aquarium to help activate the filter when adding new fish after a filter clean/water change or after using a disease treatment.