Just to clarify.
One millimeter is 1/1000 (one one-thousandth) of a meter, 103mm = 1m
One micrometer is 1/1,000,000 (one one-millionth) of a meter 106μm = 1m
One nanometer is 1/1,000,000,000 (one one-billionth) of a meter. 109nm = 1m
Nualgi's particle size is 20 to 120 Nano meters.
Diatoms are about 0.05 to 0.5 milli meters in size.