Ossubtus xinguense

koltsixx

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I got these guys a while ago but never shared anything about them even though I've wanted to. What follows is more or less a rehash of what's on wikipedia.

Ossubtus xinguense is the sole species in the genus Ossubtus in the family Serrasalmidae. It is strictly rheophilic and restricted to the rapids in the Xingu river and confirmed in the Volta Grande do Xingu but possibly occurs further upstream as far as Sao Felix do Xingu. Primarily a herbivore but macroinvertebrates have also been found in an analysis of 10 specimen's diet. In captivity shrimp, bloodworms, brine shrimp, daphnia and vegetable matter are readily consumed. Interestingly according to the wiki the females are the dominant sex and will often seek caves and guard it against all other fish. The hypothesis being it's in an attempt to find a suitable breeding location. Very cool a SD/Pacu that thinks it's a cichlid. It is parasitized by Anphira xinguense only known from Ossubtus xinguense where it lives in the fish's gills. Their intestines also are commonly infested with Rondonia rondon in what is thought a possible symbiotic relationship. Many Ossubtus are also found to have black spot disease. From the little I gleamed online it doesn't seem to be harmful to the infected fish.

Now on to my own experiences. I got three and I have a feeling they're different sexes as the anal fins are slightly different between them. Aggression is more intense then I've experienced with most other SD's. I can't speak of in comparison to Pacus as I've only had two Pacus a long time ago and their growth was ridiculous, so I rehomed them pretty fast. My experience may also be because I only have three of them but they are mixed with other SD's currently M. Fasciatus, M. Lippinocottianus? and Myleus Setiger? Sorry I'm not positive of the I.D.s of the Lippo and Setiger as there are things that give me pause in their looks versus what they were sold to me as. The Setiger are fairly aggressive amongst themselves and the other SD's but I know I've got a male and 2 females which might be affecting the dynamic of their interactions. The Ossubtus despite being smaller change up the pecking order constantly. The Setiger going from chaser to chased when it comes to the Ossubtus. Luckily it's not a constant thing but occasionally something sets things off and a quick back and forth dance happens. It can be shocking because their attack movements are weird. They attack from under and over each other darting back and forth at one another which results in occasional loud sudden splashing.

As for food the Ossubtus readily took to pellets with no issue. The Setiger are skittish eaters dashing to the surface snatching pellets and making quick u-turns to grab more which also causes considerable splashing. The Ossubtus are aggressive eaters but much more confident so much less dramatic. Another cool fish that studies you or is just constantly looking for food. If I'm in eyesight they're watching me and are quick to respond to my approach. They even respond to me looking at the tank. If my face turns to look they move to the front to see if food is incoming. They seem more aware of my looking at them then other fish. I don't know maybe I just like them so much I'm giving them more credit than they deserve. Then again, the more intricate social structure such as the female being the dominant and more aggressive sex and established territories like rocks and caves for potential breeding may mean a higher intelligence than typical of some other Serrasalmidae? Meh, I'm probably grasping at straws.

They're unfussy as far as husbandry as far as I can tell. While being rheophilic I haven't seen any struggling or stress in my tank. The tank they're in I don't believe has a lot of flow but there is a canister with spray bar, two HOB's(low ph out of tap etc so I have crushed coral in filter bags in the HOB's to stabilize it) and one powerhead. Most of the current if not all is focused at the surface of the water. My own personal preference to maximize surface agitation and promote good gas exchange for a hopefully higher oxygen concentration.

Now a pic that is not mine but may give a more accurate representation of Ossubtus xinguense
credit for pic: Rudolf Wildekamp submitted by: Benedetta Spelta website: biotopeaquariumproject
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FJB

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Very nice fish. Lucky you. Thanks for sharing.
The single photo of yours, appears to be a young male, but the photo does not show it well against your hand.
The specimen in the lower photo (not yours) is a mature female.
How long have you had your fish, and what is their size? Judging from your hand, that specimen appears to be around 4”? I may be off as you may have very large hands. But it does seem to confirm they are still young. Can you post a picture of the group, or of the other fish? Also, if you post pictures of your other sd’s, I would be happy to try to confirm ids and genders, to the extent I can. Cheers!
Again, beautiful fish!!!!
 

Kayden

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Wow very cool little fish! I love rarer types of “silver dollars” just hate prohibiting the cost of them is. Like oh these are only 50 bucks! But then you need to get 5 lol. Adds up quick
 

koltsixx

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Wow very cool little fish! I love rarer types of “silver dollars” just hate prohibiting the cost of them is. Like oh these are only 50 bucks! But then you need to get 5 lol. Adds up quick
Thank you! I actually wasn't a big "silver dollar" fan until fairly recently. I was originally into CA/SA cichlids and catfish and did keep SD's but as dithers. I was only aware of the most commonly kept SD which I believe is Metynnis argenteus. Then I saw Metynnis fasciatus and my interest was piqued because of their striking appearance which made me curious about rarer more unique looking Serrasalmidae and I was hooked. And I feel you, the need for a group does eat away at the pockets pretty fast.

Very nice fish. Lucky you. Thanks for sharing.
The single photo of yours, appears to be a young male, but the photo does not show it well against your hand.
The specimen in the lower photo (not yours) is a mature female.
How long have you had your fish, and what is their size? Judging from your hand, that specimen appears to be around 4”? I may be off as you may have very large hands. But it does seem to confirm they are still young. Can you post a picture of the group, or of the other fish? Also, if you post pictures of your other sd’s, I would be happy to try to confirm ids and genders, to the extent I can. Cheers!
Again, beautiful fish!!!!
Thank you for the compliment and the possible sex of one of the xinguense! The specimen was indeed around 4"(good eye), I believe they're around 5" now. I haven't had them long and you are correct they are young. Unfortunately, the only fish I keep track of in that regard is basically my catfish and that's only because I add them to my species list on planetcatfish.com which keeps track of the date I added them and how much time has passed. I've been trying to keep better track recently by videoing the fish floating in their bag upon arrival or in a small specimen container dependent on the size of the fish and post it to Youtube. This way the upload day is the day I received them so I can keep track of how long I've had them that way.

As for more pics the tank they're in is poorly lit and the lack of substrate makes it even worse. Otherwise, the xinguense are easy to take pics of as they're much more confident than the others but are also darker colored so they're hard to see against the black background. If I feel motivated, I may see about moving them to the specimen container to take pics there. I would like to know what the Setiger are really and the sexes of the xinguense, the Lippo I'm not as curious about and the fasciatus are easy to sex and I'm sure they're fasciatus. The "Setiger" are also very easy to sex again, I'm just not sure they are setiger. Thanks for the offer to help id, sex and again for the compliment!
 
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koltsixx

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Cool, it looks like you have 3, same as I. I'm considering getting another 3 as I am curious about breeding them. I'd be willing to dedicate a tank to them as well as the added effort to try and simulate their natural environment to the best of my abilities to see if I could make a go at it.
 
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Arraiza01

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I got about 13000 GPH as they come from rapids. Currently have 5! Great blue and purple hues and these guys.
 

koltsixx

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I got about 13000 GPH as they come from rapids. Currently have 5! Great blue and purple hues and these guys.
Dang, that's a lot of flow. lol But hey they look good so it's obviously no sweat for them. Not surprising as they are rheophilic as you and I have said. How's aggression between them? Mine can be combative at times, possibly because I only have three, and is another consideration in me getting more.
 
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