# Other Aquarium Forums > Freshwater Fauna > Characins >  Crenuchus spilurus

## diego

Hello, it does some months buy these interesting enough fish, a few Crenuchus Spilurus, savages. They are 10 individuals and accept all the food that they fact already is frozen or dry, but at the moment they are shy enough.
His origin is South America , in the basins of the Amazonian rivers, is a carnivorous fish, lives in waters with a ph from 6 to 7,2 and measures from 5 to 6 cm.
Some photos:








They live in this aquarium of 300 liters with a pair of pterophyllum altum

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## Captain Telecredible

The scapes look very wild and natural! Altums are very magnificent!

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## diego

Thank you,CaptainTelecredible , now I create a new post in ciclids zone for this fish.
regards

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## SCOPE

Can you tell the males from the females of these? i heard they spawn in caves like the apistogramma

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## ranmasatome

nice fish. used to have these guys. quite tidmid fish but really good eater. 

You should try breeding them scope..haha..  :Smile:

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## diego

Hello,
Scope , there are 5 males and 5 females. 
True, as spawning is very similar to apistogramas.
True Ranmasatome, fish are very shy and just come out from among the plants. 
Let's see if I'm lucky and breed 
yhank you 
regards

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## SCOPE

> nice fish. used to have these guys. quite tidmid fish but really good eater. 
> 
> You should try breeding them scope..haha..




haha! Yes bro, you speak out my mind.
Saw some of these at ROC.
Maybe buying some to try out. 
Just worry if they will attack apisto as they are larger in size.

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## barmby

Looking at their mouth, the size and I don't really categorise them as timid.

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## tetroid

Beautiful fish! I have a group of them in my 32 gallon tank with pencilfish. They are relatively rare in the hobby, which is a pity.

According to most of the sources I read, they are a shy, reclusive fish. However, mine aren't very shy. I think this is because they share the tank with a lot of pencilfish. They may need dithers to feel comfortable, just like apistos.

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## Heiko Bleher

Hi Guys,

this is Heiko Bleher and I just saw this between my many lectures this year. You have a very interesting fish here and maybe most of you do not know, that Crenuchus spilurus is the only freshwater fish we know now, that has infrared perception. 
Many years ago I received the order from the Geneve Natural History Musem to collect for the 1200 specimens alive and they studied them for your finding this amazing organ in their head which proved their infrered perception.
I just wanted to let you know how interesting this unique freshwater fihs is.

best regards from a collector

Heiko Bleher
www.aquapress-bleher.com

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## diego

Barmby, in spite of his(her,your) size and aspect they are very timid.

Hello Tetroid, my Crenuchus now are with Hemigrammus rhodostomus and other small fish and they continue timid and very static, though they eat very well.

Hello Heiko Bleher, is a pleasure to read you hereabouts.
Thank you very much for this information, me not it wise this information of the perception infrared and fodder that it wise few people, as you. A very interesting information, thank you very much for this information , and dedicating your time to revealing ourselves.
Thank you 
-Excuse me for my english langage I use a translator. :Well done: 
Regards

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## tetroid

That's really interesting that they can see the infrared part of the light spectrum. I knew they were genetically a little odd, but I didn't know about that characteristic. I remember reading that they had an unusual number of rays on their dorsal fin as well. It must have been hard to catch 1200 of them!

Diego, I was thinking that another possible reason yours are shy is the presence of your large angelfish. My crenuchus used to be a little afraid of my keyhole cichlid and SAE, so I had to sell them. Now they spend a lot of time hanging under leaves at a 45 degree angle. I've attached a few pictures. The last picture shows a crenuchus spilurus in quarantine. That's why he's pale. I like it because his eye is so blue.

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## SCOPE

Nice and interesting fish! and great to know their unique ability too!

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## barmby

Guys, thanks for sharing. Very interesting. and nice pictures.

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## diego

Tetroid , a very nice specimens ,and very nice photos .

I have separated the crenuchus of the altums and now already they are seen more, at the moment they prove to be very pacific, now his(her,your) companions are small fish.
It(He,She) wanted to know everything on these fish, if someone can give information I am grateful for it to him(you,them) very very much 
regards

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## tetroid

Hi diego. I'm glad your crenuchus are showing themselves more. You've probably noticed already that there isn't a lot of information about them online. Even the information you can find online is questionable. I think a lot of it is based on a subspecies of Crenuchus spilurus from Guyana. That type was first exported in the 1930s. The type that we have is a little different, and is probably native to the area around Iquitos, Peru. I'm new to them myself, but I can tell you that...

- they aren't aggressive with small fish. I keep mine with various small pencilfish, and there have been no problems
- they aren't aggressive with each other; the males establish dominance with displays, but they don't bite or harass each other, and as far as I can tell, they don't establish territories
- sometimes they like to swim together, and sometimes they like to swim apart; generally, they aren't very active, but they aren't loners and they aren't particularly shy, either
- they will eat flakes, but mine especially like cichlid pellets. As for frozen foods, they love bloodworms. They need larger food because of their large mouths
- they prefer soft water
- they seem to be smarter than the average fish, although I can't prove it
- they are very tough. When my pencilfish got sick, none of my crenuchus were affected. Some crenuchus spilurus have been living at the fish store for almost six months, and they are still ok. I would buy them all, but I don't have room.

The only site I know of that explains how to breed them is this one. The site isn't working right now, so if you can't access it, just PM me and I'll send you an archived copy. According to the article, you have to fake a dry season by hardening the water and feeding them very little for a few weeks, and then suddenly do a big water change and trick them into thinking it's the wet season by softening the water and giving them lots of food. Apparently, that starts the breeding process.

For miscellaneous information, you can check the FAQ on crenuchine tetras at wetwebmedia. It's actually just an e-mail exchange between me and Neale Monks, who is their characin guru. They posted some of my pictures as well. Here's a good article in German. If you decide to try to breed them, let us know how it goes!

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## diego

Hey Tetroid , thank you very very very very..... much :Well done:  :Well done:  :Well done:  :Well done:  :Well done:  :Well done: 
wow!!! very good information and very interesting.
Thank you

some photos

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## tetroid

I'm glad the information was helpful, diego, and thanks for the lovely photos! Your fish look very happy in that setup. As you've probably noticed, I'm a big fan of this species. If they breed for you, take pictures!  :Smile:

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## SCOPE

Very good information for such an unique fish! i will buy some this week to try out.

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## Heiko Bleher

Hi guys,

just came back from another field trip (foothills of the Himalayas) with great discoveries.

Please note: Crenuchus spilurus exist (so far) only 1 genus and 1 species - there is no subspeices described.

But I found them much wider distributed then what is written elsewhere, unfortunately would take to long to mention all locations here now, where I found the a nd collected them. Last November I found some very interesteing variants (or species) in the Inirida region and in the Boca de Cano, in Colombia, soon on my website some photos.

And, if they look more intelligent, again, then because their ability for infrared ...

All the best and keep up the good (Crenuchus)work,

always

Heiko Bleher
www.aquapress-bleher.com

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## diego

SCOPE , surely you do not repent ,we put pictures and talk about them . Thank you.

Hello Heiko, thank you very much for your information, I look at your page to see those pictures, and all the information.
These Crenuchus mine, have adapted very well, but currently there is not little fish :o: 
Greetings

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## tetroid

Diego - I don't have any C. Spilurus babies either. I tried the simulated dry season method, and they started displaying vigorously, but they didn't spawn. Next time I'll make the dry season longer and tougher.

Heiko - I'm glad you're on the case. I really look forward to seeing pictures of this new variety. I found an article in Polish that discusses their infrared capabilities and mentions you in several places. I had originally thought the weird head shape was for display purposes, but it makes sense that it is for infrared sensing. It's great that someone of your stature has taken an interest in this genus. Perhaps you'll find a Crenuchus bleheri? :-)

I only have a couple of new observations...

- perhaps it was a coincidence, but increasing the carbonate hardness of the water a little caused the fish to start displaying within about ten minutes (I used a teaspoon of Seachem Alkaline Buffer, but baking soda would probably work as well).
- they have no interest in caves, despite what the literature says. I cut up some PVC pipe and put it in the tank months ago, but they never go near it. They don't use the driftwood caves either. They prefer to hide in the roots of thick vegetation during the day, usually while facing upwards at a 45 degree angle.

Here's a video I made a while ago that shows a crenuchus spilurus display (around 0:32). I have another video that shows some other displays.

YouTube- Crenuchus Spilurus (sailfin tetra) display

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## Heiko Bleher

Hi,

nice video and nice fishes, and I like you aquariums as from what >i can see it is almost biotope-correct (except maybe for some of the Asian plants).

Yes, nice this article from Dagobert, he was a gentlemen. I was invited to give a two-day seminars in Poland during the time of still communism (1985-86). It was terrible to get a permit to enter and what a waste of search of my car. They wanted to take my Porsche apart, as they said I was smuggeling someone into the communist zone - can you believe it? I stayed all night at the border, freezing cold and no heat anywhere in those communist buildings. Next morning they called their chief and he called the factury of Porsche from where they confirmed that the front part has no engine and no place to hide someone...

Anyhow I was welcomed and hundreds of people came to my lectures and they made a beautiful cupper plate with one of the tetras I discovered - delivered by Dagobert... What memories...

I will soon write some articles on the new discoveries, but am so busy with two books to finish (everyone is waiting and daily writing me, keeping us busy answering when it will come - everyone who bought volume 1 cannot wait for volume 2, the Indian book also, everyone wants it...) and I have committed to so many seminars (biigest now in Iran...).

But you will hear from mw somewhere, keep up the good work, really nice,

always

Heiko 
www.aquapress-bleher.com

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## leeruisheng

> 


colourful finnages. Reminds me of _Betta marcostoma_.

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## diego

You're right, do not show much interest in the caves.
Thanks for sharing the video Tetroid,I like, you catch them with the fins deployed, well done.
thank you very much
Heiko, good story.
thanks for sharing your knowledge

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## tetroid

Yes, good story. I lived in Ufa, Russia for a year and a half, so Heiko's story about the officials was a little familiar. Fortunately, I didn't bring along a Porsche for anyone to take apart.  :Smile:  I'm very pleased the aquarium is almost biotope correct. That's what I was aiming for, but I had to compromise on the Asian plants, since my tank is low light.

As for the Crenuchus Spilurus, I haven't much to add except that one of the males has developed a red belly. I'm guessing that this may be a sign of dominance. I haven't seen any battles in a while, so maybe the others have accepted him as the boss. I have two females and five males. No losses since I got them. Even the ones in the fish store lasted about nine months. It's just incredible that no one wanted to buy such an interesting fish.

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## SCOPE

Nice fishes....Hope to lay hand for some more the next time....and experience on their unique breeding behaviour

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## Coryologist

Greetings. I have been doing some research on this species and was very happy to find this thread.

I have 50 of this species and have developed a deep appreciation of them. They have grown to be a good deal larger than I was told that they would.

Here is an image of one of mine, that I shot, today. Cheers. - Frank

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## dinosauricon

I currently have a pair and I personally find them more endearing than Apistogramma. I was initially considering getting myself a pair of Aggies but after having the Crenuchus for a week I think I'm going to get me somemore of them.  :Very Happy:

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## kim m

I collected them in Peru in 2008 while searching along the road between Iquitos and Nauta. Sadly I lost them even before they were shipped to Denmark. Next week I am visiting a shop that has them in stock so I consider to buy a few pairs.

In the pond where we collected them, they lived alongside a species of Apistogramma. the water was reddish/muddy and pH and conductivity was quite high. This was in the end of the dry season.

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## joemc

Hi, I know this is an old thread, but these little fish deserve to be kept top of the tetra page!
I have kept them for a while now and would agree with most of what has been posted in the two pages, they are definitely a fish worth tank space, I have been attempting to get them to produce young on and off but have not been successful yet, though I think I am getting closer with each attempt, they have not been a straight forward tetra to breed! :Confused: 
the dry season simulation seems to work most of the time to get the fish to spawn (if the fish are in good condition), with the male taking up residence in a cave and pairing up with a female, the female seems to play a much more important role in the pairing up and spawning than is given credit for, guarding the cave entrance, fending off other females etc. but getting to the fry stage, well I have not quite figured that part yet!
they can be aggressive with each other, I have witnessed females fighting and biting each other, causing damage. Males will fight over territory fins displayed and biting if one does not back off again causing damage. They are big fish, my largest male is over 9cms!
Every time I sit and watch their tank I spot something interesting in their behaviour, the way they interact with each other and the way they watch me!
I would definitely recommend that if you spot them in a shop to give them a go, my advice would be to treat them as you would dwarf cichlids and you will be on the right track

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## Shi Xuan

They are indeed very unique for tetra but sad to say that they are hardly available in the LFS. I wouldn't hesitate if I ever see them in the shops here though. 

There's a chance Poecilocharax weitzmani might be available soon but not Crenuchus spilurus.

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## joemc

that's a pity, but if Poecilocharax weitzmani become available and are in good condition then maybe they would tempt you, but these fish are not forgiving with their care, any mistakes in water quality and they will suffer. They are another cave spawner with the male guarding the eggs and displaying fantastic fins, the males will spar with each other but will do no harm.Soft acidic water, tannin stained plenty of hiding places wood, plants etc for the males to setup and defend a territory and some caves in the form of film canisters, bamboo, plastic piping etc will do for them to spawn in, set them up midway in the tank (unlike the sailfin which only ever uses a cave on ground level in my experience)

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## Shi Xuan

Yes, you're absolutely right. Poecilocharax weitzmani is one of my favorite tetra and a good substitute for Crenuchus spilurus, that is, if they ever hit our shore.

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## joemc

I have videos of my morpho tetras somewhere, I will root them out and post them if I find them, in the meantime here is one of a male sailfin encroaching on another's territory and the resulting battle, it is a bit long, but make yourself a cup of tea or crack open a beer and sit back and try and watch all of it, also notice the behaviour of the females during this time
http://www.youtube.com/watch?v=HpDvAcj9tJs

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## Shi Xuan

Indeed, males are aggressive and territorial, nothing like the tetra we are so used to see, schooling peacefully. They behave exactly like cichlids and with the size that you mentioned earlier, it makes sense that a tank of at least 3 ft is necessary to house a small school comfortably. 

Nonetheless, very nice fish. :Well done:

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## lucasjiang

The males in the video have really long fins, they look longer than what i usually see in pictures online. I assume the males must be rather mature? Also with the territorial sparring, wouldnt there be fin damage? The males in your video seem to have fins in perfect condition.

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## joemc

Hi Lucasjiang, this is what the mature males look like, most of the videos and pictures you see online only show juvie males, the fins on the fish in the video do look undamaged, but at the end of the battle when I separated them there was some damage to the fins and many scales on the body missing, I have had females fight for dominance when attempting to get the fish to spawn where females were torn to shreds and even killed when I was not quick enough to separate them!
here is a pic of a mature male
027 (2).jpg
Shi Xuan, 
here is a video to tempt you to get some morpho tetras, watch how they appear from nowhere and notice how they can take very large pieces of food, most people say they need live food to be kept alive, this group seldom were offered live food with 'tetra prima' being their main food
http://s429.photobucket.com/user/joe...028-2.mp4.html

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## lucasjiang

The morpho tetras are really nice too. I used to have a group of 8, 3 males and 5 females. Sadly they did not seem very keen on frozen food, preferring to take live tubifex worms of live daphnia. They would take the frozen food, but would not eat a lot. Unfortunately they wasted away in the end. I miss the males' sparring dances.

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