Development
Fertile lemon tetra eggs take approximately 72 hours to hatch at 28°C. The fry spend a further 24 to 48 hours absorbing the yolk sac, whereupon they become free-swimming. At this stage, the fry should be fed with infusoria or a special egglayer fry food, and frequent partial water changes (around 10% of the aquarium volume every 24 to 48 hours) initiated. After 7 days, the fry should be ready to feed upon newly hatched Brine Shrimp. The fry appear to be almost transparent at first, with the exception of the eyes, and do not begin to develop the 'lozenge' shape of the adult body until the differentiation of the finfold into the unpaired fins is complete (around 4–6 weeks). Once this process is complete, the fishes are ready to take sifted Daphnia. Maintenance temperature for the fry should be carefully and slowly reduced to around 25°C once the fishes are thus recognisably miniature versions of the adults. The first signs of black colouration on the unpaired fins may take a further two weeks of more to being manifesting themselves, and it will not be until the fishes are at least 12 weeks old that they will fully represent miniature versions of the parents. Even at this stage, the black colouration of the unpaired fins will be incompletely developed, and it will not be until sexual maturity is achieved (approximately 8 to 9 months after hatching) that the black border on the anal fin will become a reliable gender differentiation characteristic.
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