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How do you / can you sex - Sturisomatichthys sp. "Columbia"?

I've 4 that are approx 4 inches.

I can't see any head bristles - 2 seem wide in the middle region & 2 seem straight-er.

I've attached some pics (Hopefully)







[Mod edit: Put direct links to pictures, rather than thumbnails - makes it easier to view the pictures --Mats]

Yes, it looks like you have some females and some males - there is really only one sure way to find out: Keep them well fed and see if they breed!

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Mats

Thanks! - But what's the diferences between M&F - That's the main thing I'm trying to learn from you guys that Know!!

MatsP wrote:Yes, it looks like you have some females and some males - there is really only one sure way to find out: Keep them well fed and see if they breed!

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Mats

I'm going by what you mention: Females are "fatter", males a bit more slender. This is certainly the case for Sturisoma, and I think these are closely enough in the "fish family tree" to match that principle.

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Mats

Ah! I see - Thanks!

If they're not "Fat" - What can be the other differences?

Has anyone bred these?

Cheers!

Again!

MatsP wrote:I'm going by what you mention: Females are "fatter", males a bit more slender. This is certainly the case for Sturisoma, and I think these are closely enough in the "fish family tree" to match that principle.

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Mats

I am not aware of any breeding reports. This is mostly because these animals typically come arrive in small numbers as bycatch. I believe the top photo in your first posting shows two males and two females. Beside the females being more plump, males will develop the typical cheek odontodes as they come into spawning condition.
I would expect them to spawn in typical Sturisoma fashion on a vertical flat surface. That said, if I had a group, I would also place some bamboo or PVC sections on the substrate (like you would for Rineloricaria) just to see if they show any interest in them.
The breeding tank should be simple. I would use a 30-40 gallon with a thin, fine sand substrate and good filtration to include a medium-sized powerhead. I would cut two pieces of slate to about 4 inches wide by 10-12 inches long and lean them against the back of the tank in opposite corners. Place 2-3 bamboo/pvc spawning tubes on the substrate (they need to be open at both ends) and then finish of with a decor of angled branches throughout the tank.
-Shane

I don't know if it is of any significance but in pic 1 the fish on the left (fat) has rounded pectorals as opposed to the fish on the right (thinner) where the pectorals are very pointed.

Shane - good set-up advice, covering a number of spawning possibilities