There are many reasons for fish to die. Your fish, most likely died of old age or you were not feeding it or not feeding it enough food. It could also be a diease. If fungus was growing over the rocks, or the tank, it could be possible he/she died of that.
because the black knife ghost fish is nocturnal and will most likely hide all day.
These fish grow large and are not social animals so unless you have a very large tank I would not advise you to put two together.
Several years. It is more reliable to say that Black Ghost Knives are mature at 15-18 cm (6-7 inches) long.
Surprisingly there are many fish with electric abilities, most of them live in brackish water and it is believed that the electricity is a means of communication.
knife
No Only if they stab you with a knife.
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.
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!
Your fish can not be pregnant so don't panic. They are egg layers so their eggs are fertilised and the young hatch out in the water not in the fish. Black Ghost Knife Fish (Apteronotus albifrons) grow to over 20 inches long and need a very large aquarium (at least 6ftx2ftx2ft) and are extremely hard to breed so the chances of you manageing it with your lack of knowledge (of the species) are very unlikely.
Black moors are a variety of goldfish which are egg layers so they can't get pregnant.