Very short term as all the above fish can grow in excess of a foot in length.
no
black ghost knife fish gets nutrients and energy from the food it eat
No.
The maximum length of the black ghost knifefish is 40 centimetres
they can be 49cm.
Not really, Oscar is going to grow to about 9 inches so It will most likely eat/kill the Goldfish sooner or later.As for the Ghost knife im pretty sure you can but not certain
No.
Yes it can
Black Ghost Knife Fish are semi-agressive. They should be fine though. The angelfish should be fine.
fish about 5in or 4in lowest
Yes if its the only one?
Depends what store!