A method for determining error in a chemical indicator reading of an aquatic environment monitoring system, the method comprising: illuminating a first region of a first chemical indicator of a chemical indicator apparatus with a first reference illumination from an optical reader of the aquatic environment monitoring system; measuring a first reference response from the first reference illumination; comparing the first reference response for a deviation from a predetermined trusted reference value stored in a memory of the aquatic environment monitoring system; determining a first confidence value from said comparing the first reference response to the predetermined trusted reference value; illuminating a second region of the first chemical indicator with a first measurement illumination; measuring a first measurement response from the first measurement illumination; and generating a confidence adjustment based on the first measurement response and the first confidence value; wherein said generating a confidence adjustment includes combining the first confidence value with one or more addition confidence values to determine a total confidence level for the measurement response; wherein the one or more additional confidence values are each based on one or more errors in the aquatic environment monitoring system, each of the one or more errors including an error value related to a condition selected from the group consisting of a degradation in a chemical indicator due to photo-aging, a degradation in a chemical indicator due to water-aging, an illumination imbalance related to an optical reader , a degradation of a light source of an optical reader , a displacement due to friction between a chemical indicator apparatus and a monitoring unit, an error intrinsic in a chemical indicator , and any combinations thereof. illuminating a first region of a first chemical indicator of a chemical indicator apparatus with a first reference illumination from an optical reader of the aquatic environment monitoring system; measuring a first reference response from the first reference illumination; comparing the first reference response for a deviation from a predetermined trusted reference value stored in a memory of the aquatic environment monitoring system; determining a first confidence value from said comparing the first reference response to the predetermined trusted reference value; illuminating a second region of the first chemical indicator with a first measurement illumination; measuring a first measurement response from the first measurement illumination; and generating a confidence adjustment based on the first measurement response and the first confidence value; wherein said generating a confidence adjustment includes combining the first confidence value with one or more addition confidence values to determine a total confidence level for the measurement response; wherein the one or more additional confidence values are each based on one or more errors in the aquatic environment monitoring system, each of the one or more errors including an error value related to a condition selected from the group consisting of a degradation in a chemical indicator due to photo-aging, a degradation in a chemical indicator due to water-aging, an illumination imbalance related to an optical reader , a degradation of a light source of an optical reader , a displacement due to friction between a chemical indicator apparatus and a monitoring unit, an error intrinsic in a chemical indicator , and any combinations thereof. <EOS>