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Discussion Starter · #1 ·
I special ordered blue tetras from my LFS. Got them still in the bag so couldn't check them too closely. They were also kind of faded from the trip. Anyway, one is clearly different (with the stripe). I'm thinking it's an SAE but not sure. Any ideas?
 

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Discussion Starter · #3 ·
I don't think it has barbels but at this size it's hard to tell. I see what you mean about similarity in this pic. The blue tetras in the pic aren't as colored as others in the tank and they don't have a horizontal stripe like this fish (though the pic seems to show one?). This mystery fish also has prominent white tips on the dorsal and pectoral fins. The blue tetras also have a noticeable red/orange patch on the top of their eyes that this one is missing.

It definitely schools with the tetras but tends to stay in the bottom half of the tank.
 

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Definitely not an SAE.

They all have the black lateral stripe, it's just the other's are faded. I would say all specimens in the pic are of the same species.

Just upon first glance, to me, the face/mouth area says they are of the Knodus genus.
Check this database, look through the Knodus species and try to pin point which species yours are. Give the fish some time to color up.
Characiformes

The only Knodus species I am familiar with, is Knodus borki (scientific name of the blue tetra). And if the species you obtained is anything like them, those little guys are mean, fin nipping even non-elongated fins of larger fish.
Seeing how you purchased them under the name of blue tetra, that may be even more to think of them being of the Knodus genus (misidentified or similar species collected in same location?).

There is another fish that is misidentified and just sold as the same fish under the name "blue tetra". It's scientific name is Boehlkea fredcochui and it looks almost exactly the same, but this one is supposed to be more peaceful in comparison.

I used to really want to keep the "blue tetra", but didn't want to risk getting a mean fish, so I didn't. If you are after that blue sheen/shimmer, that the blue tetras have, I might suggest Blue Kerri tetra (purple emperor), emperor tetras, or rainbow emperor tetras. Another option may be dwarf neon rainbowfish (Melanotaenia praecox).
 

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Look at the fish with the stripe.
Look almost halfway between the dorsal fin and the tail, a little closer to the tail.
I think I see an adipose fin. This is common in Tetras, not in Barbs or their relatives, or most other aquarium fish.
I am not sure if this is a blue tetra, but it is not a SAE.
 

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I special ordered blue tetras from my LFS. Got them still in the bag so couldn't check them too closely. They were also kind of faded from the trip. Anyway, one is clearly different (with the stripe). I'm thinking it's an SAE but not sure. Any ideas?
Looks like a long-band rasbora maybe.

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I special ordered blue tetras from my LFS. Got them still in the bag so couldn't check them too closely. They were also kind of faded from the trip. Anyway, one is clearly different (with the stripe). I'm thinking it's an SAE but not sure. Any ideas?

Found it! Ureyi Tetra. Notice the red eye in the fish in your photo.
 

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Discussion Starter · #9 · (Edited)
OK, almost a week now and I'm still convinced it's not the same species as the others. It stays in the lower half of the tank when the others come up to the surface to feed. None of the others have developed such a prominent black stripe and their fin tips are not nearly as white as this one.

I do agree that it's not an SAE - so some kind of tetra - maybe Ulreyi. I thought blue tetras were raised not wild caught, so I wonder how the odd one got mixed in. I've never seen Ulreyi for sale in a store either.

As to my choice of blue tetra, yes they should be Knodus borki. I have a school of 11 plus this striped fish in addition to a school of 13 pristellas. They all school together and ignore my pair of angelfish and the betta. There is some intra-species chasing, but nothing unusual for tetras. Not to say this will last forever, but so far so good.

Thanks for all the input!
 

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This is a common thing to happen and it is easy to see how the dealer may have sold you the wrong fish and never known it. Thinking of ponds full of fish it is easy to see how one fish may get mixed with the other pond. Simple human error or nature? Maybe a bird plucked one out of the pond and while flying over the other pond, lost it? So now that you have spent a good deal of time trying to sort out what fish you have, would it be fair to expect the dealer to spot the problem when he is bagging a couple hundred fish to ship? You may have the correct fish or not. But it happens, even in the best of deals.
At some point the fish may get large and mature enough to know for sure---or maybe not!
 

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How many did you special order? Just the 4 in the pic? Or were there 11-12 in this acquired group?

The ones in the pic definitely are not Knodus borki (blue tetras), nor are they Ulrey/Ulyrei tetras (Hemigrammus ulreyi), not long-band rasbora either. Just saying.
Blue tetras (Knodus borki) are all wild caught for the most part.

No expert, but judging by the markings/pattern and physical features, all the fish in the pic look to be of the same species. For the prominent black stripe and whiter edges on fins on the one fish, I would chalk that up to that being the only male (sexual dimorphism) or at least the only dominant or mature male. The others still appear to have identical, but fainter black markings and white tipped fins. Another possible explanation may be the others are sick or just stressed, but I think unlikely. As for the different feeding behaviors, I'm not quite sure, maybe it just need more time to settle in, or possibly the others are malnourished and so are more eager to feed than the bolder colored one. Does this one in question still interact with the rest of the group as if it really is one of them (same species, or at least same genus)? Do these new tetra interact with the other blue tetras?

If you could get a clearer picture of the ventral fin or get a clear pic of the dorsal fin extended so you can count the rays, that can narrow your search. If you can find out where they were collected, that would narrow down things to just a few species.

From the picture, I still think they are some species of the Knodus genus.
 
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