The advantage of the FISH is its simple and rapid performance as well as high
sensitivity and reproducibility. The method had a great contribution to the research on
the internal structure of the flocs, which enabled to put into the practice aerobic and
anaerobic granular sludge, which has excellent settling ability.
Apart from many advantages, FISH-based techniques are cost intensive thus
their widespread use is seriously hampered by the inability of many laboratories to
carry the high cost of fluorescence microscopes and molecular probes. Moreover, ex-
isting studies are merely focused on qualitative identification of bacteria in aerobic
and anaerobic granular activated sludge and the biomass of bacteria cannot be deter-
mined in a practical way. It seems advisable, however, to initiate close cooperation
between biotechnologists and engineers responsible for the operation of wastewater
distribution systems in the field of implementing FISH-based methods in the future,
especially in the area of practical quantitative usage.