An unopened bottle of Seachem ParaGuard Broad Spectrum Treatment - 500ml (No expiry on this stuff.) ParaGuard™ is the only fish and filter safe aldehyde based (10% by weight) parasite control product available. Unlike highly toxic and difficult to use formalin based medications, ParaGuard™ contains no formaldehyde or methanol and will not alter pH. Does not expire (http://www.seachem.com/support/forums/forum/general-discussion/1486-expiration-date-of-medications). (For more information, see link below.) Retails for $16.99 at PetsAndPonds.com (see link below). If interested, please email (no text/calls, thanks).