One of the most immediately recognizable features of this species is the rounded caudal fin of the vast majority of males (in most other species, there are upper and lower fin ray extensions). As in many other Apistogramma, several naturally occurring color forms of this species – whose sex is influenced by both temperature and pH – exist.
- Mainly Rio Ucayali and Rio Yavari, west of Iquitos, Peru.
- Males up to 3 1/2 in (9 cm); females smaller.
- Typical Apistogramma
- Prefers livefoocis, but may also accept commercial preparations.
- Layout as for other Apistogramma species. Apistogramma nijsenni is less demanding than most of its closest relatives in its water chemistry requirements. Temperature range: 75-82 F (24-28 C); slightly higher for breeding.
- Breeds in typical Apistogramma fashion. Peat filtration and soft, acid water recommended. Hatching takes 3-4 days Experiments have shown that at 68-73 F (20-23 C) all eggs develop into females; the ratio of males begins to increase from 73.6 F (23.1 C) with 100 percent male offspring being produced at 84.4-89.6 F (29.1-32 C). Hatching rates are low in hard water (around 16 percent), rising to around 83 percent in soft water.