In monogamous species that provide biparental care, partners with similar behavioural types generally have a better reproductive success than dissimilar ones. The pattern of assortative mating for behavioural type is thus often interpreted as resulting from a mate choice process. However, an alternative process is also possible when the partners become similar through postpairing adjustments (behavioural convergence). The disentanglement of these two nonexclusive mechanisms is an important evolutionary question. Only sexual selection based on behavioural similarity before pairing can explain the maintenance of the behavioural type variability. In a previous study, we reported the existence of behavioural convergence for aggressiveness between partners in convict cichlids Amatitlania siquia, a monogamous tropical fish. We tested herein the assumption of mate choice based on behavioural similarity for aggressiveness using either short-term binary choice or long-term group level pairing. Pairing was not based on behavioural similarity between potential partners. Choosing a behaviourally compatible partner is a complex task because it requires profiling the potential mates. Individuals would thus achieve higher fitness benefits from choosing a partner on more conspicuous criteria (such as size for instance) and then attempt to increase partner similarity by convergence after pairing. Sexual selection does not appear to drive the maintenance of aggressiveness type variability in convict cichlids.