Focus can deliver any medication internally by binding the medication to its polymer structure. The advantage is that the fish can be medicated without contaminating the entire aquarium with medication. Fish find Focus appetizing and it may be fed to fish directly or mixed with frozen foods. Focus contains nitrofurantoin for internal bacterial infections. Marine or fresh water use. DIRECTIONS: Use alone or in combination with medication of your choice in a 5:1 ratio by volume. Feed directly or blend with fresh or frozen food. Feed as usual, but no more than fish will consume. Use at every feeding for at least five days or until symptoms clear up. Contains polymer bound nitrofurantoin