I'm dealing with this pond water for analysis of chemical parameters such as (ammonia, nitrite, nitrate, phosphate...etc.) using a visible spectrophotometer

while I was preparing standard curves for each analyte I tended to use distilled water or reagent blank for zero reading acc. to the standard method that I follow in my lab

But when I started working on field samples; they look different from the standard solutions prepared in the lab

the samples are colored and turbid

is it true to use the same water sample as a blank in this case _ a separate blank for each sample_

or acc. to methodology, water sample+ all reagents except that producing the color of reaction as a blank

to obtain accurate measurement by removing background color or turbidity of sample that may absorbes hight at the same wavelenghth of the analyte of interest?