A collection media assembly for receiving one or more particles from a volume of fluid within a fluid composition sensor , the collection media assembly comprising: a housing ; a particle collection slide comprising a transparent substrate and a collection media disposed upon an upper surface of the transparent substrate , the collection media configured to receive one or more particles from a volume of fluid received through a fluid inlet ; and at least one alignment feature ; wherein the housing defines an open lower end configured to interact with an imaging device , such that the one or more particles received by the collection media are visible through the transparent substrate from the open lower end of the housing ; wherein each of the at least one alignment features is configured to engage a corresponding element disposed within the fluid composition sensor so as to constrain relative movement between the collection media assembly and the corresponding element in at least a first direction; wherein the housing comprises an upper cassette portion and a lower cassette portion ; wherein the upper cassette portion is configured to direct the volume of fluid toward a receiving area of the collection media ; wherein an opening extends through the lower cassette portion ; and characterized in that the opening is arranged to define a line of sight to the one or more particles received by the collection media for the imaging device , the line of sight extending through the lower cassette portion , and in that the lower cassette portion comprises one or more features configured to receive and secure the particle collection slide across the opening , so that the opening defines distinct first and second opening portions located on either side of the particle collection slide , the distinct first and second opening portions configured to enable the volume of fluid to flow through the collection media assembly . a housing ; a particle collection slide comprising a transparent substrate and a collection media disposed upon an upper surface of the transparent substrate , the collection media configured to receive one or more particles from a volume of fluid received through a fluid inlet ; and at least one alignment feature ; wherein the housing defines an open lower end configured to interact with an imaging device , such that the one or more particles received by the collection media are visible through the transparent substrate from the open lower end of the housing ; wherein each of the at least one alignment features is configured to engage a corresponding element disposed within the fluid composition sensor so as to constrain relative movement between the collection media assembly and the corresponding element in at least a first direction; wherein the housing comprises an upper cassette portion and a lower cassette portion ; wherein the upper cassette portion is configured to direct the volume of fluid toward a receiving area of the collection media ; wherein an opening extends through the lower cassette portion ; and characterized in that the opening is arranged to define a line of sight to the one or more particles received by the collection media for the imaging device , the line of sight extending through the lower cassette portion , and in that the lower cassette portion comprises one or more features configured to receive and secure the particle collection slide across the opening , so that the opening defines distinct first and second opening portions located on either side of the particle collection slide , the distinct first and second opening portions configured to enable the volume of fluid to flow through the collection media assembly . <EOS>