Abstract: Many microfloral factors of the fish nursery ecosystem act to the favour or detriment of fish larvae at night. In this experiment, 2 replicates each of three treatment freshwater ponds were tested with varying nutrient regimes to assess their impact on phytoplankton populations at night. The first treatment-A (200 m² surface area supplied 70 kg ha ¹ month ¹ pig manure only), treatment-B (200 m² surface area supplied 70 kg ha ¹ month ¹ pig manure, 50 kg ha ¹ month ¹ N.P.K [15:15:15] and 30 kg ha ¹ month ¹ Urea) and Treatment-C (1500 m² surface area supplied 1150 kg ha ¹ month ¹ commercial grade 40% crude protein compounded feed). Water replenishment for Treatment A was daily tidal deluge from the New Calabar River while that for treatment B and C was from column well and occasional rains. For 6 months, 36 contrasting phytoplanktons were nocturnally encountered in the whole experiment. Economically important pond flora such as Coelastrum microporum, Pediastrum tetras, Scenedesmus quadricauda were obtained from all treatments while singular occurrences were Coelastrum proboscigera, Closterium venus, Chlamydomonas olifanii, Merismopedia glauca, Cyclotella striata and Melosira italica (treatment-A); Closterium reticulum, Closterium macilentum, Pleodorina carlifornica, Scenedesmus acuminata, Treubaria triappendiculata, Aphanotheca clathrata, Gleocapsa limnetica, Microcystis pulverea and Spirulina gracile, Trachelomonas hispida, Cyclotella antiqua, Fragillaria intermedia, Melosira varians and Tribonema viride (treatment-B); Selenastrium bibriaianum, Volvox globator, Spirulina principes, Euglena wangi, Phacus longicauda, Phacus pleuronectes and Synedra ulna (treatment C). These indicate their potential mono- and polyculture as well as the varying nutritional and ecological fortune derivable from these nutrients in practice.