Can you keep a black ghost knife fish with paradise fish?

It is generally not recommended to keep a black ghost knife fish with paradise fish. Black ghost knife fish are solitary and territorial, while paradise fish can be aggressive and nippy. In addition, black ghost knife fish require different water parameters than paradise fish. Black ghost knife fish prefer soft, acidic water, while paradise fish prefer hard, alkaline water. Therefore, it is best to keep these two species of fish separate.