Cattail and knotgrass were planted in the tanks with the configuration
similar to the surface flow wetland system and tested
from June 2005 to September 2005. Cattail was growing in six tanks
with size of 0.6m(width)×0.6m(depth)×6m(length) (two tanks
of 3m length in series) (Fig. 3). Knotgrass production was investigated
in three 0.3m (width)×0.3m (depth)×3m (length) tanks.
Recycled wastewater from the fish production tanks was pumped
into these tanks to supply plants with water and nutrients. The TN
concentration in the supply water was about 2mg/L. Plant biomass
was harvested on an irregular schedule depending on the time of
year and amount of growth. Cattail was cut to a 10 cm height and
knotgrass was cut to a 5cm height. The biomass was measured and
recorded in approximately three different months for calculating
the growth rates.