The fluorescence signals emitted from phycoerythrin and phycocyanin have made them suitable for use as indicators to detect cyanotoxins such as microcystins in drinking water. A study examined the nature of the biliproteins' fluorescence signals regarding their real-time character, sensitivity and the biliproteins' behaviour in different treatment stages (of water) in comparison to microcystins. The fluorescence signals' real-time character was confirmed by fluorescence measurements, as they can be carried out without having to pre-concentrate the biliproteins.