Knife Fish Anyone?

I’m building a sort of oddball community, and yesterday I found a ghost knife and glass knife for my collection. They’re so awesome, but I have barely seen them since I got them home. I realize they’re shy, but was just wondering if anyone has kept these fish, and would share anything about the experience. What were the favorite foods, how long before they become more comfortable, interactions with other fish, rate of growth etc. My tank is a 65g and moderately planted, with lots of TX holey rock- lots of hidey-holes! I took my time acclimating them yesterday, and have seen the glass knife eat, as well as the two African butterflies I added, so I feel like the transition went well enough.

 

I could be wrong, but I think two knifes will need a bigger tank.

 

Hi. Some of them can get really big!!!

 

I could be wrong, but I think two knifes will need a bigger tank.

No you’re absolutely right. These are both quite small but they’ll need something bigger fairly soon, especially the ghost.

 

You don't see them very much because they are nocturnal. They are so cool!!!!

 

Hi. Some of them can get really big!!! What kind do you have?

Ghost knife and glass knife- the ghost knife can get huge, but Google says it takes them a while. That’s a question I have for folks who’ve had them- how quickly do they grow? I’m looking forward to setting them up a tank of their own! As far as I can tell, the glass knife stays fairly small in comparison, but still gets much bigger than his current size- about 6”, the ghost is only about 4”, so I have a bit of time. I have 2 juvie leopard ctenopoma who will go to the bigger tank too- it’ll be a fun project!

 

Ghost knife and glass knife- the ghost knife can get huge, but Google says it takes them a while. That’s a question I have for folks who’ve had them- how quickly do they grow? I’m looking forward to setting them up a tank of their own! As far as I can tell, the glass knife stays fairly small in comparison, but still gets much bigger than his current size- about 6”, the ghost is only about 4”, so I have a bit of time. I have 2 juvie leopard ctenopoma who will go to the bigger tank too- it’ll be a fun project!

Good luck with your project. Hope all goes well.

 

Black Ghosts grow quite quickly up to maturity at about 10”, then they slow down a lot. I’ve had a few over the years and have fed them mainly prawns and cockles. Some will occasionally take dried food from the bottom, but most wont. And depending on how ‘happy’ they are, especially with the tankmates, they might come out in the light... or not. You might have to feed it at night.

I haven’t kept the glass knifes.

 

Some 18" Black Ghost Knives on Youtube.

 

From my research, they are timid and shy due to poor eyesight and shyness. I'm hoping you have tall plants. Apparently, whenever the electrical field indicates an open space, they will avoid it if possible. Open space equals scary space where big hungry things may be.

They should become social with you. Signal when feeding is and they will learn the signal. They can be out competed for food so he careful. I'm picking one up in the next few months.

Also, your knives are very new. Give them some time to get used to their new life.

 

From my research, they are timid and shy due to poor eyesight and shyness. I'm hoping you have tall plants. Apparently, whenever the electrical field indicates an open space, they will avoid it if possible. Open space equals scary space where big hungry things may be.

They should become social with you. Signal when feeding is and they will learn the signal. They can be out competed for food so he careful. I'm picking one up in the next few months.

Also, your knives are very new. Give them some time to get used to their new life.

Aren't they nocturnal?

 

From my research, they are timid and shy due to poor eyesight and shyness. I'm hoping you have tall plants. Apparently, whenever the electrical field indicates an open space, they will avoid it if possible. Open space equals scary space where big hungry things may be.

They should become social with you. Signal when feeding is and they will learn the signal. They can be out competed for food so he careful. I'm picking one up in the next few months.

Also, your knives are very new. Give them some time to get used to their new life.

How would you signal?

 

Aren't they nocturnal?

Yes but not to a hard extent. Most nocturnal fish will be active during part of the day, especially if it means an easy meal.

The most common signal ive seen is tapping the water or the glass.

 

Yes but not to a hard extent. Most nocturnal fish will be active during part of the day, especially if it means an easy meal.

The most common signal ive seen is tapping the water or the glass.

Don’t tap on the glass though, it’s very stressful to fish... Just drop the food in, they’ll detect the vibration of most hoods being opened, and smell the food as soon as it’s in the tank. They won’t have a problem finding it.

BGs are nocturnal, but when you only get fed once a night you’ll come out to get food during the day... if it’s safe. They won’t if they’re in with cichlids of any size for example.

***Important Bit.... I just looked up glass knife. We call them green knifes in the UK which is why I overlooked the obvious.... they’re electrical fish too.... which means you can’t keep one with a black ghost. The BG will kill it. You can’t keep an electrical knife (Gymnotiformes) with any other electrical species (other knifes or Mormyrids).

 

Don’t tap on the glass though, it’s very stressful to fish... Just drop the food in, they’ll detect the vibration of most hoods being opened, and smell the food as soon as it’s in the tank. They won’t have a problem finding it.

BGs are nocturnal, but when you only get fed once a night you’ll come out to get food during the day... if it’s safe. They won’t if they’re in with cichlids of any size for example.

***Important Bit.... I just looked up glass knife. We call them green knifes in the UK which is why I overlooked the obvious.... they’re electrical fish too.... which means you can’t keep one with a black ghost. The BG will kill it. You can’t keep an electrical knife (Gymnotiformes) with any other electrical species (other knifes or Mormyrids).

Oh wow really?! I didn’t realize the glass was electric! How come they had them together at the LFS? Just short term and still little? O gah now to decide which to return.... I love the BG but he’s going to get awfully big... I was planning to accommodate him with a bigger home, but not for a little while... dang. Oh man and I’m gonna hafta net one. Jeez

 

Maybe there were a few of them in the tank? Once one gets settled it won’t tolerate another. They’re totally peaceful with other fish ime. They have a powerful bite but will only use it as a last resort. But anything with an electrical field....

How big a tank were you thinking of going to. BGs don’t bend much... big ones have to do 3-point turns... My last one grew to 16” in a 2ft wide tank and was kinda cramped.
There are several knifes that are a lot smaller....

 

Maybe there were a few of them in the tank? Once one gets settled it won’t tolerate another. They’re totally peaceful with other fish ime. They have a powerful bite but will only use it as a last resort. But anything with an electrical field....

How big a tank were you thinking of going to. BGs don’t bend much... big ones have to do 3-point turns... My last one grew to 16” in a 2ft wide tank and was kinda cramped.
There are several knifes that are a lot smaller....

Want to list them?

 

Hmm ok, not so many that are ever available. Even the Glass/Green Knife grows to 16” or so.
The African knife, Xenomystus nigri, can grow to a foot but usually stays smaller.
The Barred knife, Steatogenys elegans, is available very occasionally. A beautiful one, also grows to about a foot.

 

From my research, they are timid and shy due to poor eyesight and shyness. I'm hoping you have tall plants. Apparently, whenever the electrical field indicates an open space, they will avoid it if possible. Open space equals scary space where big hungry things may be.

They should become social with you. Signal when feeding is and they will learn the signal. They can be out competed for food so he careful. I'm picking one up in the next few months.

Also, your knives are very new. Give them some time to get used to their new life.

Maybe there were a few of them in the tank? Once one gets settled it won’t tolerate another. They’re totally peaceful with other fish ime. They have a powerful bite but will only use it as a last resort. But anything with an electrical field....

How big a tank were you thinking of going to. BGs don’t bend much... big ones have to do 3-point turns... My last one grew to 16” in a 2ft wide tank and was kinda cramped.
There are several knifes that are a lot smaller....

Well neither was a planned purchase, which is where my problem started! Ha I went in to get more wisteria to fill in a corner where I topped mine off. Walked out with 4 oddball fish... again. My current tank is about 3.5 feet, but there’s a used 150 gallon up at the LFS for 150$. It’s about 5’ across and probably 2.5 wide. I’m learning now that the glass knife likes to school, which is unusual for electric fish...the glass at least comes out more, so I might have more luck netting him. I can’t support a school of them to grow out in my current tank anyway. So. Much. Sadness.

 

A 5 x 2.5 would be better than a 6 x 2 for a BG, imo...

 

I had a black ghost knife for a couple years. He was shy and nocturnal for the first month or so then once he got used to the tank he was very active and a lot of fun to watch. He was a very aggressive feeder and knew when it was feeding time every night but he never caused any problems with any of my other fish and spent most of his time in plants or caves.

 

A 5 x 2.5 would be better than a 6 x 2 for a BG, imo...

That’s what I was thinking- square would be ideal bc there’s nowhere to get pinched, but that’s into financial dreamland for me!

 

Well neither was a planned purchase, which is where my problem started! Ha I went in to get more wisteria to fill in a corner where I topped mine off. Walked out with 4 oddball fish... again. My current tank is about 3.5 feet, but there’s a used 150 gallon up at the LFS for 150$. It’s about 5’ across and probably 2.5 wide. I’m learning now that the glass knife likes to school, which is unusual for electric fish...the glass at least comes out more, so I might have more luck netting him. I can’t support a school of them to grow out in my current tank anyway. So. Much. Sadness.

Elephant nose fish also like to school. I suspect we pick and choose which schooling fish to declare a large number required. The common pleco also likes to school. Nobody ever recommends a school of trinidads though.