Effects of bacterial-algal combination on the growth performance of silver carp and bighead carp and water quality in the aquaculture environment

Li Cuiyun; Yang Zhenbo; Yang Dongfeng; Yang Zhenyan; Qin Qing

doi:10.20154/j.cnki.issn1672-9692.2025.08.007

Abstract：This experiment aimed to investigate the effects of a microalgae-bacteria combination on the growth performance of silver carp(Hypophthalmichthys molitrix)and bighead carp(Aristichthys nobilis)and on aquaculture water quality.Under large-surface aquaculture conditions,2 400 fish with an average body weight of(41.35±0.50)g(silver carp to bighead carp ratio 3∶1)were randomly divided into four groups:Control group(CO group),T1 group,T2 group,and T3 group.Each group had three replicates with 200 fish per replicate.While the treatment groups received one of the following additions to the aquaculture water every 15 days:T1 group-6.25 mL/L Chlorella,T2 group-0.75 mg/L EM bacteria(effective microorganisms),T3 group-a mixture of 6.25 mL/L Chlorella+0.75 mg/L EM bacteria.No bacteria and algae were added in CO group.The trial lasted 90 days.The results showed that the weight gain rate,specific growth rate and fattening degree in T3 group were significantly higher than those in the other groups(P<0.05).The survival rates of each experimental group were significantly higher than that of CO group(P<0.05).At 45,60,75 and 90 days,the contents of total nitrogen(TN)and total phosphorus(TP)in the aquaculture water of each experimental group were significantly lower than those of CO group(P<0.05).At 45 and 60 days,the permanganate index(CODMn)of the aquaculture water in each experimental group was significantly lower than that in CO group(P<0.05).At 30,45 and 60 days,the ammonia nitrogen(NH3-N)content in the aquaculture water of T1 group was significantly lower than that of CO group(P<0.05).At 30 days,the NH3-N content in the aquaculture water of T2 and T3 groups was significantly higher than that of CO group(P<0.05),and at 45 days,it was significantly lower than that of CO group(P<0.05).At 30 days,the nitrate nitrogen(NO3-N)content in the aquaculture water of each experimental group was significantly lower than that of CO group(P<0.05).At 15 days,the content of nitrite nitrogen(NO2-N)in the aquaculture water of T2 and T3 groups was significantly lower than that of CO group(P<0.05).The study demonstrates that both Chlorella and EM bacteria effectively purify aquaculture water for silver carp and bighead carp.Furthermore,the synergistic purification effect of the Chlorella-EM bacteria combination is stronger than that of either microalgae or bacteria alone.Specifically,the combination more effectively reduces the content of TN,TP,NH₃-N,NO₂-N,and CODMn in the aquaculture water.