Biofilm formation is one of the crucial limiting factors which influences the microalgae production because sufficient light conditions for microalgae cultivation are required. One of the possibilities, how to prevent biofilm formation, is to properly set-up hydrodynamic conditions. Generally, when a minimum value of wall shear stress at the internal surface of the illuminated area is reached, then biofilm can be removed. Studies of the relationship between hydrodynamics and biofilm removal for tubular photobioreactor system were performed in the laboratory stand for biofilm removal under flowrate in the range 1 – 40 L min-1 in DN20 glass/PMMA tube. The biofilm removal was observed for the wall shear stress values ranging between units and low multiples of tens of Pascal. These novel results are recommended to be respected during photobioreactor´s operation to avoid biofilm formation.