Data for various physical, chemical and biological parameters were collected in 1983-84 at the Babakan Fisheries Station of the Institute Pertanian Bogor, Indonesia, during the first experimental cycle of the Pond Dynamics/Aquaculture Collaborative Research Support Program (PD/A CRSP). The station is located 6.6 degrees S, 106.1 degrees E and is at 220 m above mean sea level. Climatic conditions lacked seasonal attributes and showed little variation over an annual cycle. Mean air temperature was 27.3 C, rainfall 1.3 cm/day, evaporation 0.35 cm/day, and wind speed 0.8 m/sec. Clouds and water vapor limited light at ground level. Means between 29 and 30 moles of 400-700 nm photons/m2/day were reported during these first cycle experiments. The station and drainage basin are characterized by highly leached and permeable volcanic soils. Ponds are susceptible to high rates of water loss due to seepage. Surface water used for pond culture had low total alkalinity (21 mg calcium carbonate/l). Algal productivity was low in ponds (0.8 C/m2/day). Excursions in vertical distribution of dissolved oxygen during 24-hour periods had small amplitudes leaving ponds well oxygenated at all times, and substantiating low rates of algal productivity and suggesting little detrital metabolism. However, amounts of phosphorus, nitrogen and photo synthetically active radiation were adequate for potentially greater algal production. When alkalinity was raised to 37 mg calcium carbonate/l, algal productivity increased (1.2 g C/m2/day). This indicated that algal productivity was limited by the availability of inorganic carbon. Under these conditions Nile tilapia (Oreochromis niloticus) yield was poor: approximately 600 kg/ha for grow-out periods of about 145 days. Concentrations of un-ionized ammonia were too low to substantially retard fish growth. These baseline data were used to design experiments for higher fish yield using lime with fertilizers in the second year of CRSP experiments. (Author abstract).