Despite potential advantages of artificial reefs in areas where natural coral reefs have degraded, relatively little research has been undertaken in Eilat to improve our understanding of the major factors governing the development of reef biota. We report on the first study in a series aimed at increasing our knowledge of the effects of morphology, substrate type, and location on the succession of reef organisms. The development of stony corals and fish communities associated with two types of constructions was examined, which were both made of aggregates of limestone rocks: one randomly aggregated (RA) reef comprising relatively small rocks and an orderly aggregated (OA) reef composed of relatively big rocks. Communities were censused every 4–6 months for more than 4 years, with a final coral census being taken after 100 months. The OA reef attracted significantly more fish species and a higher number of individuals than the RA reef, and reached its carrying capacity faster (30 months versus 50 months). In contrast, number of reef-building corals on the RA reef was significantly higher (in terms of both species and colonies) than on the OA reef, and the plateau was not even reached after 100 months. We conclude that in the Gulf of Aqaba, (1) for recreational purposes, small reefs (of a few cubic metres) may serve as attractive sites because they support relatively rich fish communities, (2) larger rocks, larger interstices and larger reef size induce higher species richness and greater numbers of fish, and (3) structural complexity, as measured by fractal dimension, is an important factor for the development of reef-building corals. Copyright 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.