Sternopygus macrurus

[vintage_fish]

Fishbase says they get 141cm.

I unintentionally ended up with one through a pretty long story, and am currently housing it in a 3'x5' (1m by 1.6m) pond in the garage. I realize this is FAR too small a space for him, and is only sufficient *right now*, while he's currently 16" (41cm) long, and even still I'd like him to be in a larger space as soon as possible.

Some questions about the species:
-How fast do they grow?
-How much do they eat?
-Can they be trained onto frozen or prepared foods?
-What, if anything, can be housed with them?

Note, also, that this is not my first knife, nor my first delicate fish. I've been keeping fish for 20 years. My garage is a fish room, and I breed fish for fun and sale. I've got something on the order of 25 tanks, not all of which are running at the moment, ranging from just a few gallons to 100 gallons.

I'd love any details on these guys; there's not a whole lot of information available about them online aside from scientific journals about their electric abilities.

 

[vintage_fish]

Also of note, the pond is approximately 200 gallons / 757 liters.

 

[aranos]

I have to say I've never kept the species myself, but according to everything I've read about the genus, fishbase is wrong. I've attached a chart displaying the total length of 142 adult specimens of S. macrurus (averaging 52.5 cm). I’ve also heard that R. marmoratus is supposed to be the largest SA knife (maxes out at about 100 cm), so 141 cm for a gold line knife seems way off to me. So you probably don’t have to worry about how fast this guy is going to grow. As far as foods go, I’ve never had a problem training gymnotiforms to eat frozen bloodworms, etc. Since they eat a lot of benthic invertebrates and larva in the wild, I can’t think of any reason they couldn’t eat the same stuff in captivity. For roommates, since you’ve kept knives before you know to steer clear of fin nippers and other aggressive fish. The only advice I might add is to make sure you don’t put anything in there that will out-compete him for food. I had a little school of yoyo loaches in with some R. rostratus, and had to take them out because the greedy little f**kers would always snatch up the bloodworms before the knives even knew it was feeding time. So maybe stay away from really active benthic predators, and throw in some mid/top level swimmers that are too big to get eaten. Oh, and post some pictures!

Hope this helps,
wes.

 

[vintage_fish]

This is EXACTLY the kind of information I was looking for, thanks!!

Do you happen to have Figure 2 of that table, or a link to where you found it?

This gives me a bit of hope that I might be able to house this guy long-term - I was actually gearing up to contact some friends at local-ish public aquaria to find a long-term home for him. I did not actually plan on keeping the fish, due to his potential size - but I would like to if I reasonably can. Obtaining this fish was actually quite inadvertent.

Right now, I have two angelfish in the pond with him. They were getting seriously chewed up by a pair of Ctenopoma, and it seemed like a nice place to put them for now. So far he hasn't eaten them <grin>.

I have before raised and reproduced ghost shrimp as food animals for my fish; I may just have to do that again. The knife had previously been fed exclusively on earthworms for a month, and judging by the gut analyses listed on fishbase, worms aren't a major food source for these guys, so I'm pretty concerned about that. I have plenty of frozen shrimp for my other fish, but no live shrimp that I'm willing to use as feeders right now.

I guess I'd better set up another tank, eh?

I've been pining for a Polypterid, but I fear that might be too aggressive at grabbing food to be housed with the knife.

 

[aranos]

Got the chart from this article:

Crampton, W.G.R., Hulen, K.G., & Albert, J.S. (2004) Sternopygus branco , a new species of Neotropical electric fish (Gymnotiformes: Sternopygidae) from the lowland Amazon Basin , with descriptions of osteology, ecology and electric organ discharges. Copeia 2004 (2) 244-258.

Can't post the whole pdf cause of the file type restrictions, but fig. 2 is attached. If you want the whole file I could email it to you. It has a nice breakdown of stomach contents for S. Branco, which might help you figure out what to feed your knife.

 

[vintage_fish]

I would be absolutely delighted if you might email me the .pdf file!

My email address is vintage_fish (AT) yahoo (DOT) com

Thanks again!

-Sabrina

 

[aranos]

sent

 

[vintage_fish]

Thank you!!