The black ghost knifefish is a tropical fish belonging to the ghost knifefish family. They originate in freshwater habitats in South America where ranging from Venezuela to the Paraguay–Paraná River, including the Amazon Basin. They are popular in aquaria.

M. boesemani is also available in the aquarium hobby, where it is prized for its excellent colors and peaceful demeanor. The color pattern is completely different from most other forms of rainbowfish, as it has a half orange-red rear and a bluish-grey or purple front which in some specimens is almost defined perfectly. M. boesemani will often grow to lengths that exceed 10 cm (3.9 in) if given the right food and water conditions. Like most rainbowfish they are capable of adjusting their color intensity. Their color intensity may be a sign of mood or health. Generally more intense is seen during night time. They are kept best in groups due to their community and friendly nature and can be easily kept with many different species of fish, including some tetras. They are relatively hardy fish that prefer weakly alkaline pH conditions. Good tankmates include other rainbowfish, barbs, tetras, corydoras, snails, gouramis, danios, discus, guppies, swordtails, and loaches. However, smaller freshwater shrimps in the genera Caridina and Neocaridina may be viewed as prey. Ghost shrimp, vampire shrimp, amano shrimp, and bamboo shrimp can live with them. Always adult shrimps have added first then baby rainbowfish. Care must be taken to give hiding places for shrimp and open spaces for rainbowfish.

The oscar is a species of fish from the cichlid family known under a variety of common names, including tiger oscar, velvet cichlid, and marble cichlid. In tropical South America, where the species naturally resides, A. ocellatus specimens are often found for sale as a food fish in the local markets.

The Copper Oscar Fish most important aspect of mixing any aggressive cichlid in an aquarium is the tank size. It has been said that if you have an aquarium large enough, you can mix any fish.