The maintenance of marine mammals requires a close and careful interpretation of water quality from the chemical standpoint. Present "easy" methods of analyses have inherent difficulties and technical problems both in the laboratory and in sampling, which may hinder proper interpretation. This paper deals with selected chemical parameters (eg. Ammonia, Nitrates, Nitrite, Sulfates, and organic chemicals, chlorine, ozone and amines) which can be influenced or masked during simple analysis. The use of LaMotte, Hach, Delta, and Standard Methods for Water and Wastewater Analysis are compared for accuracy and ease of procedure. A suggested set of minimal chemical parameters are presented for both open and closed systems and the interpretation of results discussed. Experimental results using minimal chemical treatment and simple filtration in conjunction with "bio-filtration" are discussed. Present results indicate that the use of "bio-filtration" may alleviate or reduce the necessity for chemical treatment of system waters in closed systems.