Note – 1 US gallon = 3.79 liters. I keep meaning to convert throughout the text in these posts and hope to do so soon. But here is the formula for those who need it in the mean time. 🙂 Hope it helps.
Jan. 2010: For those of you using clear plastic tubes for your fish but need some shade, break clean, red clay flower pots (never used) in half as best you can and place them over the top of the tube. You can still see the fish from the side but it will get some shade from the lights. A quick fix if you do not mind the look. Ours is loving it.
Oct. 24, 2009. A paragraph added near the end from someone talking about his 16 year old Black Ghost Knife!
Sep. 2009. She is now around 12 inches!
Note: I do respond to comments on my old posts.
OK, finally the post…..
We have had her for nearly 2 years now. When we got her she was only around 1.5 inches at best. Now she is a whopping 10 inches long and still growing. And she is fat. She is no longer that svelte, sliver of a fish that she originally was in the petshop.
I finally got a video of her (above). Right now it is simply a few seconds of her swimming in her tube. But she is so unusual compared to other fish on how she swims so I thought it would be neat to put it up for those who are unfamiliar with this fish. Future videos will be of her eating and playing with our fingers. It is taking longer than I expected to get those but they will come.
She is now housed in a 55 gallon tank on a cinder block stand. We knew she would be getting large when we got her so we were prepared to make the jump in tank size before her health was threatened. But she certainly grew fast. Her diet now consists of live meal worms, frozen blood worms, and the occasional sinking shrimp pellet. You can also use beef heart. When you use animal meat, it needs to be very lean. Animal fat is not great for fish for long term feeding. Best to stick to water critters.
The tank is still being decorated in these pictures. We plan to add more hidey holes and such soon.
One of the joys of having this fish is that she takes food from your hand. This fish looks intimidating but she is gentle. Twice a day one of us reaches into the water and hands her one meal worm at a time. We now grow our own since she may eat as many as 15 in one sitting. For the bloodworms we can now hold a frozen chunk above her and as they thaw, the worms rain down for her to suck up. Sometimes she takes the entire chunk and works on it herself but she loses quite a few that way. The other fish (mostly tetra varieties) in the tank flock over and grab them up as they drift past her. We have some fat little fish in this tank. The hand feeding can be annoying at times if you are in a hurry since one cannot just dump in some flakes and run. You also have to be extremely careful not to have perfumes, aftershave, soap, and the like on your hands since these fish are very sensitive to water quality.
Black Ghost Knives love to have a tube to stay in during the day. They are nocturnal so we do not see her swimming about out of her tube much until all the lights are out. But her tube is transparent so we do get to watch this fascinating fish at any time. BGKs do not like bright light so if you do use a transparent tube, it is recommended to cover the top with something to shade her from the tank lights or leave the lights off. You can still see in the tank with lights from the room (the latter not a good idea if you have live plants). Our tank has a set of lights for each side so we leave the lights off on her side where her tube is located. It is neat to see what fish in the tank like the bright side and which stay in the shady side.
BGK vision is very poor. They have a very light electric field that they use to sense thier surroundings. If you move her tube with her in it, she will swim perfectly with the tube no matter what angle you tip it. This fish can be seen swimming upside down, sideways, tail tip up, and every which way as she scans the tank. She has one long fin stretching the length of her ventral side that undulates in a wave for swimming or making sudden, full stops. She looks very similar to an eel but without the flexibility. Her back tends to be fairly rigid.
It is hard to find a large transparent tube for these fish without paying too much. We used a polycarbonate tube from a bird-feeder with all of the parts removed. The ports where the bird seed came out of left a few holes in the side that really works well for feeding and water circulation. We often dangle the worms through these holes and when she is hungry, we may see her put her nose into these holes looking for food. As she became bigger, we had to get larger bird feeders to take apart. This largest one was special ordered for just the tube and no parts. It is much cheaper than getting an entire bird feeder this size if you want a nice quality plastic that will not leech anything into the water. Let me know if you try this by leaving a comment. I like to know if this works for other people and helps me keep motivated to update. 🙂 Note: more tube ideas added near the end of the post.
There are many small fish (a variety of tetra, pearl guaramis, killi fish, cori cats, etc.) housed with this fish. She has never attempted to eat any that we can see. Not even neons. She ignores them unless they enter her tube. Then she rapidly shoos them out with nose bumps.
I recommend this fish to anyone who has medium to advanced fish keeping experience and is willing to dedicate a large tank to this fish. It is a myth that tank size will limit the size of the fish without harming it. The fish WILL grow. If it is in a tank that is too small, it just might not grow right (such as a bent spine) and still get big. If you buy one, avoid any that are laying flat on the bottom. They should be moving around, never laying down. They are starving, stressed, and possibly on their last leg if they are laying down. Get them a hidey hole, test your water, and try a different feeding method if you have one like this. Maybe turn the lights out.
If you click on the picture abive for its full size (I hope that works) it should show her face a little better. Her eye shows up white because the flash reflected. Usually her eyes are black. She is going through another growth spurt and is now up to taking over 20 good sized meal worms twice a day. I hope she does not start eyeballing the tetra (added sep 4, 2008).
This picture (left) finally captures her head. She never holds still long enough to get a great picture. Also the light on her side is rarely on. You can see eel-like features such as the “tubes” for nostrils and that jaw. Once again her eyes are white from the camera. The white patch below her jaw is part of her normal markings. She also has an almost white stripe on her nose, ending on the chin. Here her mouth is slightly open. She just chased a cori out of her tube. “Get off my lawn ya damn kids!”
Added September 11, 2008
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There are other kinds of knife fish but the BGKs are the friendliest and, if I remember right, not as related to the other knifes. If you are the type that wants one that will ravage other fish, then go with a different variety of knife fish than the BGK. Leave this one alone. If you wish to have more than one, be sure it is a big tank. But having one that will hand feed is really neat. Maybe try one that you can focus on first.
For more details on the species visit http://fishprofiles.com/files/profiles/387.htm This is one of my favorite sites for researching fish profiles. Eventually I will post a list of wonderful sites of this type for cross-referencing your fish.
For more fish profiles and information links, visit my Page O’ Links site listed on the right. Eventually the fish links will be another blog when I get them all together. Still adding.
Rain often will play with Mike’s hand after feeding. She gets excited and swims through his hand or back and forth against it. Her fin speeds up and it looks like she is just having fun. I hope to add a video of this and of her feeding soon.
Here she is swimming upside down, back and forth against his hand. Notice the cute white triangle under her jaw.
Feel free to let me know about yours or ask questions! I love to hear about your fish and learn from good ideas!
Here is a story by Jim. It is in the comments but I wanted to be sure people caught this. This is in his words:
” I bought a BGK about 30 years ago! Piggy started out 2 inches and was almost 2 feet when he died 16 years later. He was also very social, more so as he got bigger. Started him off in a 10 gal. tank and moved to a 20, then 55, then 120, then finaly into a 340 custom. The last 7 or 8 years he mainly ate fish with some shrimp and some veg. – he loved endive. For over 10 years he shared a tank with a very mild Red Belly – he was about 5 inches when I introduced them and over a foot when he died. They got along fine and would chase each other around at feeding time, jocking for the best spot I guess. Both would spend a lot of time people watching. I had a hollow ceramic “tree trunk” in the tank as a hidie hole and he “moved” it so he could look out into the room. I moved it back several times because it looked funny, but he always moved it back so he could watch so I gave up.
After Piggy died, I tried a couple more Knife fish but never had any luck with them afterword, the both died within a couple years. I hope you can enjoy yours for many years to come.”
Thanks Jim! (Oct, 2009)
Added September 18: More tube ideas.
So I am noticing many people hitting this post are looking for ideas for tubes for their BGK. Here is another idea to go with the bird feeder tube mentioned in this post.
Get 2 or 3 rectangular pieces of plexiglass that is taller, longer, and much wider than your fish. If you use two pieces, prop them up in and upside down “V”, wedged into the gravel to hold them up. It does not have to be a circular tube. To make them stay more permanent and to not worry about collapse, use aquarium-safe caulk. Do not use regular caulk, it will kill your fish. You can get aquarium caulk at some pet shops or at Lowes and maybe Home Depot (at least it was there a few years ago). The latter two are much cheaper than at the pet shop. Be sure it says safe for aquariums or do not use it, even if water proof. Caulk the top of the upside down “V” or make an upside down “U” with corners by using 3 pieces. Or make a solid square using 4 pieces.An advantage of the “U” shape is that you can pile rocks on top for some shade. Be sure the roof rests on the sides if you do this for support. You do not want the roof to cave in. I would make the top piece for the roof wider than the fish is tall so she can flip sideways and upside down.
Be sure to let the caulk dry for the recommended time. Maybe a little longer to be extra sure. Maybe soak it after that to be even more sure. I am paranoid. 😉
This way you can build a new “tube” as your fish grows. This is what I will have to do if mine keeps growing. And she is growing. I am glad I decided to raise meal worms!
Bottle: If you have the means to cut glass, take a clear wine bottle and cut off both ends so you have a glass tube. Be sure the ends are rounded smooth so the fish does not injure itself. Do not wash the bottle with soap but rinse very well.
Any other ideas? Let me know!! Use any of these ideas? Let me know! (It keeps me motivated to update)
An easier idea!:
For this idea I am not sure how safe this plastic is under water as far as leeching but here it is. Just get a 2 liter (or whatever size fits) bottle for water or soda and cut off the ends. Viola! A tube. You can even cut out feeding ports. File down the edges so they are not so sharp. Gets full of algae? Just make a new one! Woohoo!
You may need to stop it from floating by pushing a layer of gravel into it.
Another idea for small fish from a reader: Glass Candle chimneys. Sigh, I do not know what these are called but you place this glass tube-like thing over your candle. It is open on both sides and thick in the middle. When I get the time to research this more I will post the right name plus a reader picture as well. No fair when life prevents blogging, huh?
For more stuff to learn to do go to my main site https://virtuallyamy.wordpress.com/. Notice there is more than one page of blogs to go through….and more coming! Yay (again)!
For another unusual pet read about my electric blue crayfish. I Just got this bad boy recently (early Sept).
Or check out a post on bettas https://virtuallyamy.wordpress.com/2008/09/07/betta-fish-look-at-the-bubbles/
For more fish and tank related stuff, go to my Categories listed on the right and click on fish from the drop down menu. (Hopefully it will show all.)
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