Let us start with the fact that this fish gets very bit and needs a big tank. This as much as 24 inches in length in the wild but less in a tank. and because it is not very flexible, it needs a tank clearly wider (front to back) than than the fish os long.
This fish is also tolerant of a range of conditions as it is found in the wild in a variety of parameters. "
Range: South America: Venezuela to Paraguay and ParanÁ Rivers, also the Amazon Basin of Peru"
Next, this is a nocturnal fish and needs a place to hide during the day. Finally, this fish has a weak electrical sense. It is not dangerous in that respect but it uses this sense to navigate murky waters in the dark. It also allows it to detect it's prey. If there are other fish in the tank with the same ability this can cause issues. Also if there is any random electric current, or any interference for such, in the tank this too can cause problems.
If you have not read this before, I suggest you do so now:
https://badmanstropicalfish.com/black-ghost-knife-fish/
This fish should not be exposed to ammonia or nitrite for sure.