Water samples were collected from the outlet of the fish tanks
three times per week for the measurement of TSS (total suspend
solids), TAN (total ammonia nitrogen), NO2-N (nitrite-nitrogen)
and PO4-P (orthophosphates). The TRO of the fish tanks in RAS-O3
was measured daily. Details of the sampling process and measure-
ments are described in Li et al. (2014): TAN, NO2-N and PO4-P
were measured using an Alliance Futura instrument (Sociele AMS
France, Frepillon, France). TRO was determined by colorimetric
N,N-diethyl-p-phenylenediamine (DPD) method (Aqualytic, Lan-
gen, Germany).