The aim of this terminated project was the detection of a potential mutualistic relationship between coral-associated fishes and reef-building corals. The main focus was on coral-associated gobies. Damselfish were included with respect to adaptation of fish body form to the physical restriction of coral interbranch space. Coral-associated gobies show specific relationships to various growth forms of corals, including massive, plate-like, encrusting and branching corals. The genera Acropora, Stylophora and Pocillopora are the most frequently occupied. These corals are inhabited by gobies of the genera Gobiodon, Paragobiodon, Pleurosicya and Bryaninops and by damselfishes of the genera Chromis and Dascyllus. In this project we investigated the potential fitness advantages for corals that have a goby partner and the potential of natural selection for different body shapes among gobies and damselfish that dwell different coral growth forms. We applied underwater video monitoring for etho-ecological studies, in situ and ex situ experiments and morphological (geometric and traditional morphometric) techniques to achieve the main goals of the project, the observation of potential mutualisms and particular adaptations between corals and associated fishes. The results have been published in more than 10 scientific papers (most of them have been published yet and can be found in "publications")