Cent percent allotriploids were induced by heat shocking (42°C for 3 min) of 2·5 min old (post-fertilization)Oreochromis mossambicus eggs fertilized with (homozygous) red tilapia milt. Control diploid hybrids were red (orange) in colour. A few triploid hybrids displayed more patches of black pigmentation. Hence red and black colours are regarded as co-dominants. Survival of the allotriploids was higher than that ofOreochromis mossambicus autotriploids.