Amiscience's low-cost phycocyanin primary calibration standard is designed and formulated for Amiscience's handheld fluorometers or other manufacturer's equivalent, and is even suitable for submersible probes. Each calibration standard is stored in a 100mL bottle. One simply adds 100mL of water into the bottle to re-constitute the standard before performing the calibration on handheld fluorometers. The solution can be further diluted to 500mL as required for calibrating submersible probes.