The ghostknife is the best fish i have. It's around a year and a half old and has grown to over 23 cm. It started eating flake and blood worm, but now eats bloodworm flake, and earth worms once a week. It has taken out about 10 neons in the past. You should feed their main meal at night, I use my reading lamp so I can see. It will pull an earthworm out of my hand and rip it to pieces. I feed it 3 worms which are bout 7 cm each. Great fish to have and very impressive to friends. Make sure there is a dark area for them, mine is under a long bit of driftwood. pH should be just below 7 and avoid moving them from tank to tank cause they very sensitive scales. I'll have to get a 2 meter tank in the next year for it because its growing is not slowing down. You can train them to lie in your hand at night as well. Good filtration, water changes and lots of protein will ensure that yours will grow quickly!
I have kept this species as a single specimen for several years. While many of the comments concerning the gentle nature of the fish and its predatory practices are reassuring they are hardly what I found to be the case with this fish. Yes it attacks and devours many small species while it too is a juvenile or young adult. As it ages, however, the size of fish is not as important. More important is the species of fish and the perceived threat to territory and food supply. Mine is currently 46 cm TL. It exhibits aggressive (damaging to the point of deadly) to many geophagus species. As well, it is often dissatisfied with larger angel fish and severums. Mine is in an 850 L aquarium. It needs an enormous amount of space to develop properly and live to its life span. The fish enjoys cover—it comes from well vegetated, fast moving waters. The use of stem feeders as floating plants at the surface of the aquarium provide a suitable environment for ample daytime (lights on) viewing. A well planted tank will always bring this fish out in the daytime.
My black ghost is one of the most beautiful fish I have ever seen. I have one, who stays in a very good sized bell with my algae eater and my elephant nose. The black ghost cannot see and neither can the elephant nose very well, so they give off electric shocks almost through the water to find their food. I have been told that sometimes having the elephant nose and the black ghost together can be a problem because of those shocks, but so far so good. I have had my ghost longer, about five months now, and my elephant nose just about one month. Another lesson I have learned about these beautiful fish is that they have a slight appetite for fish eyes, as strange as that might sound. I work at a pet store and with the black ghosts we had cory cats. Well, the ghosts ate some of the eyes from the cory cats. They are still doing fine, but just as an advisement, I would probably shy away from having very small cory cats in your tank. Mine are a good size and have been there a lot longer than the black ghost.
*Disclaimer* Although this is all true below, it is NOT typical for these fish! I bought one of these guys awhile back, and he was at most 5 cm long at the time. I know it was a stupid buy because I put him in my planted 200 L community tank with neons and guppies and the like. Like usual, I never saw him during the day for the first few weeks. The reason for this is that I don't like putting fake glass things in my tank, so he hid in the plants and rock formations. At first he only ate frozen brine shrimp from a turkey baster at night, but after awhile he learned to eat with the rest of my fish! I always gently tap the top of my tank as I feed, so that my fish know it's feeding time, and, being the smart fish that he is, he learned that food came when I did this. Now he's always out during the day, floating around and checking stuff out. When it's feeding time he goes vertical, face up and out of the water, searching for food. Afterwards he goes vertical again, face in the rocks, looking for missed food. He hasn't eaten any of my other fish or shrimp yet, even though he's over 15 cm now. He's by far my favorite fish in the tank, being one of the most active and most unique looking fish in there. It's crazy how different he is from every other knife I've ever seen.
My black ghost Montezuma seems to buck the shyness trend indicated by some others. It still spends 3/4 of its time in the cave, but can also frequently be spotted scouting the tank in the middle of the day. I put its sociability down to several factors: 1) The aquarium is heavily planted and has duckweed (Lemna minor) floating on the surface which helps disperse the lighting; 2) He's learned to be handfed outside of his cave; 3) He's in an understocked tank with adult guppies providing a frequent source of baby fry - yum yum. The only other fish in the tank are a pair of anti-social fire eels.
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