The effects of optimal sources and concentrations of major nutrients (supplying N, S, P, K+, Na+, Ca2+, Mg2+,and inorganic carbon) and organic buffers on growth and secondary metabolite accumulation in Scytonema ocellatum strain FF-66-3 were determined. Nitrate, phosphate, magnesium, and sulfur had no specific stimulatory or inhibitory effects on scytophycin accumulation within the range of concentrations that supported optimal growth. Calcium concentrations greater than those required for growth (0.1 mM) stimulated scytophycin accumulation. Sodium carbonate concentrations in excess of 0.25 mM strongly inhibited growth. Ammonium (2.5 mM) inhibited both growth and product formation. 3-[N-Morpholino]propanesulfonic acid at 3-5 mM effectively controlled pH and facilitated both growth and product formation.