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Wow... I'm glad I bought seven of them, then. Now I've got some fish for the top level of the tank, and interesting fish at that.
I love the little pencils, but I'm having trouble sexing them. I guess once they color up a little, it will be easier for me to tell.

Oh, and I'm done with stocking my tank now.

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And when he gets to Heaven, to Saint Peter he will tell: "One more Marine reporting, Sir! I've served my time in Hell."

In the case of your One-Lines, it might prove a bit difficult Sirbooks ... if I recall correctly, they don't exhibit the same level of obvious gender dichroism that Beckford's do. However, they are incredibly slender fish, and wonderfully graceful in the right setting ...

Post pics soon ... especially if you have Vallis thickets for them to pose against, because they look good against a Vallis thicket upon account of their 45° head-up orientation ...


Panda Catfish fan and keeper/breeder since Christmas 2002

The only information that I've been able to find regarding sexing states that females are thicker (duh), and don't have the bright red anal fins that males have. That doesn't sound right, as I have yet to see much color at all on their anal fins. Surely they don't mean caudal? I know that several of my pencils have red on their caudal fins, but others don't. From looking at my pencils, I've seen the red-finned fish engaged in *almost* nipping each other, much in the same way as male lemon tetras do. I'm assuming for the time being that these guys are the males.

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And when he gets to Heaven, to Saint Peter he will tell: "One more Marine reporting, Sir! I've served my time in Hell."

You wouldn't believe the fun I had trying to find decent photos on the web of One-Lined Pencils, with male and female segregated so they could be differentiated by sight if there existed appropriate visual cues. Plenty of photos of single fish (of indeterminate gender) accompanied by copious maintenance notes, but precious little on breeding (at least during the quick glances i took over each of the pages Google returned).


Panda Catfish fan and keeper/breeder since Christmas 2002

Okay, this sounds crazy, I know. But I have actually seen several one-lined pencilfish (Nannostomus unifasciatus) eating algae from plant leaves! We just got some of these awesome little Characins at work, so I’ve been observing them. I hadn’t known of any pencilfish that were veggie-lovers, so imagine my surprise when I saw several of these skinny fish picking off green algae! They’d hover over to an algae-laden plant (live or plastic, it didn’t matter) and sway in the current, along with the leaves. Then, they’d choose a spot, and peck away slowly, consuming tufts of algae. They did not spit it back into the water column, but would steadily consume more. Shoot, I’ve never seen any other tetra-like Characins eating algae. Anyone else out there witness anything like this?

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And when he gets to Heaven, to Saint Peter he will tell: "One more Marine reporting, Sir! I've served my time in Hell."

My Beckford's Pencils may sometimes supplement their diet with vegetable matter: I've noticed them hovering around Java Moss and Amazon Swordplant leaves in a manner similar to the one you've described for the One-Lines. The modus operandi is as follows: hover staring at a given spot for anything up to 30 seconds, then pick at that spot, even if there doesn't appear to be anything edible on that spot to human eyes. Then, choose another spot, repeat the performance. It's entirely possible that they can see tiny creatures living among the algal threads that we can't, and are eating those.

Possibilities include:

[1] The Pencil Fishes are genuinely eating the algae by choice;

[2] The Pencil Fishes are eating small organisms, browsing the algae as the easiest way to capture them, and consuming the algae too, because [2a] they actually like it, or [2b] the taste of the small organisms sufficiently masks the taste of the algae for them to eat that too.

Once upon a time, after all, I'd have agreed wholeheartedly with those textbooks that say Otocinclus are exclusively herbivorous. Having kept them for over 10 years, and seen them eat animal matter quite happily, including live Bloodworm as immortalised in my photo a while back, I now characterise them as primarily herbivorous aufwuchs grazers. Your Pencil Fishes could be aufwuchs grazing in a similar manner, but with a preference for the small organisms living therein.



Panda Catfish fan and keeper/breeder since Christmas 2002

i have to say, in the short time i've been keeping beckford's, i have noticed them picking at almost anything in the tank, including algae on the plants. they do 'stare', don't they? as Cali mentioned, it may be micro-organisms rather than the algae which is initially attracting them...

I've read that Trifasciatus pencilfishes are good algae cleaner fish, so it wouldn't shock me that Beckford's are too.

Oh yeah, Pencilfish are great little algae munchers. I've seen my Beckfords in tug of wars with hair algae, really determined to pull it off.

Pencilfish are very popular with planted tank people for a reason They are pretty good at keeping small plants like Java Moss and Riccia clean.

I've said it before you'd be amazed at the amount of fish that do eat algae, just most don't do it 24/7 like say Ottos, so are never going to help a tank with a bad outbreak, but they do help with keeping things staying nice in a well run tank.

Dwarf Gouramies are another suprising species that will tuck into algae and things like Hydra. Rams are great for snail eggs. African Butterfly Cichilds great for snails. Mollies very efficient algae eaters.

Once you get a tank that's really densely planted you'd be amazed how the fish changes behaviour. Random cross tank swimming is almost elimanated (with the exception of most Tetras) and more purposeful "natural" behaviour takes over. The fish are always hunting and scavenging, some in surprising ways. The best bottom feeders I have are my Cherry Barbs. Rams love roots (guess there's a reason they like the bottom so much), even the Angelfish has given up staring at the wall and prowls around hunting for something usually fry or Rainbow eggs.

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Some days you're the pigeon and some days you're the statue.

Remember that age and treachery will always triumph over youth and ability.

While I've never seen Glowlight Tetras go after live algae in the library tank I maintain, this may only be because I haven't had that much time to watch them. They absolutely love algae wafers, quickly beating every other fish in the tank to them (including Plecostomus).