The hydrochemical state of the rearing pond for Pseudosciaena crocea larvae was studied, and the results are summarized as forllows:1. The ranges of main hydrochemical parameter values during the rearing period are:pH: 7. 8~8. 1, NH3 -Nt: 0.13~4. 17mg/L, NH3 -Nm : 0. 005~0. 167mg/L, No MN: 0. 04~ 0. 162mg/L and COD 5. 23~ 11. 53mg/L.2. The water quality can be effectively improved and maintained in a good state by adding appropriate amount of algae solution in the ponds near estuary.3. The water quality certainly changes after feeding, especially the concentration of NH3 -N increases significantly. The changes of feedstuff species influence water quality greatly.4. The concentration of NH3-N in the area of larval fish aggregation is higher than that of non-aggregation, also, which shows that excreta decomposition is one of the factors increasing the concentration of NH3-N.