Nanoparticles exhibits size and shape-dependent properties, thus each with unique character and use. Caulerpa prolifera, Sarconema filiforme, and Padina tetrastromatica; were collected from Suez Canal, Egypt, for silver nanoparticles (AgNPs) fabrication. The algal extract was added to an aqueous solution of AgNO3, and AgNPs synthesis was monitored with an hourly interval by UV-Vis Scan. Physical factors, pH, temperature, and light were studied. Depending on the surface plasmon resonances (SPR) bands and λ-max, AgNPs synthesized using Padina at pH 7, 30 ⁰C after 168 h in the dark were characterized. λ-max was at 430 nm, XRD indicated the formation of AgNPs, HR-TEM images mainly showed spherical particles with size ranging from 5 to 25 nm, and Zeta-potential insinuated AgNPs stability. FTIR analysis of the algal extracts indicated diverse phycoconstituents. This study reveals a diverse response of phyconanofabrication to physical factors, and Padina tetrastromatica is a green and cost-effective AgNPs factory. [ABSTRACT FROM AUTHOR]