Jenynsia Onca Biotope tank build

[junebug]

Hi All!

I'm new around here, and buzzing around about some toads I want, but I thought I'd share this fish tank I've been working on.

I'm involved with wild type species preservation for assorted varieties of wild type betta (I breed them and plan to give away one sibling pair free to someone who also wants to breed them at least once a year when I've got things going better). Well, I also LOVE livebearing fish, and I came across these beauties on an auction site not long ago. I just had to have some. They are Jenynsia Onca, a new species to the hobby, with very little information available on them. I'm hoping to breed them and observe them, compile research, and publish it at least on my own sale website if not in an e-mag or similar.

I splurged and bought a 15 gallon Clear for Life tank, azoo plant substrate, and used some driftwood I've been collecting. There's a manzanita burl in the tank, along with a root piece of some wood or other, probably oak or manzanita given the locations in which I collect.

Bill knows this already, but for the rest of you: I'm huge on planted tanks. Why? I hate water changes LOL. Also I live in a small apartment and some of my tanks are crammed in weird places where you can see them, but they're a pain to get to. This one, for instance, is in my kitchen. Behind my island, under a window. Given how much I love NPTs, and given I had a great experience with an appropriately planted 10 gallon natural light tank before, I went with natural light only for this one.

I'm also a huge fan of biotope tanks. I truly feel that the best way to keep fish is in a home environment that mimics their natural one. So I did a bunch of research, found about three scraps of information on how to set up a Rio Uruguay biotope tank, and for the rest, I'm kind of flying by the seat of my pants lol.

The tank isn't finished yet. I'm going to add oak leaf litter this week, and I have more plants coming in to keep the water clean for me. I'm also hoping to add a catfish species that is found very commonly in and around the Rio Uruguay.

Anyway, here's the fun part: PICTURES!

[Mentat]

Good luck with them ! Those are rare; even Fishbase has very little information.

[junebug]

Fishbase is actually where I got about half of the very little information that I have. At least it gave me a location for them. From that, I was able to construct an idea of what plants, fish, and environmental factors they might encounter in the wild.

I located a few species that are native to Uruguay and likely to be found in the same areas as these guys. I'll be getting, if I can find them, a trio of hisonotus aky cats, which are cute little emerald green guys, similar to oto flexilis and often found alongside them. If I can't find the hisonotus, I'll try for otos, as they are common all over that part of south america.

I've been observing the behavior in these fish, since there's not a lot of info out there, and so far, having an overabundance of males hasn't presented a problem.

[deranged chipmunk]

Very cool! I love a good biotope tank! I didn't like oak leaf litter in my tank. It throws up too many diatoms. But then again, the only livestock I keep in that planted tank is snails. Lol. I'm more of a fan of ial or cacao leaves. I love the deep dark blackwater look though, as opposed to the lighter version.


Education is the most powerful weapon we can use to change the world ~ Nelson Mandela

[deranged chipmunk]

Can you post a pic of each gender??


Education is the most powerful weapon we can use to change the world ~ Nelson Mandela

[junebug]

Hiya Bill! :P Nice to see you in the fish area lol.

The fish have totally clear fins, so it's hard to determine gender in pictures. I have one clear shot of the largest male, but you can't see his gonopodium in it because of the angle. Let's just get some cool fish pics on this thread to oggle anyway, though

I haven't added the leaf litter yet. I put in the rest of the plants today, or at least most of them (I owe this tank two more Uruguay swords but it seems silly to order just two plants from my supplier, so it'll have to wait until I need more lol.) I wanted to see what kind of room I had left. I'm also looking for a moss to coat pieces of the driftwood, but I was impatient obviously, and put the wood in the tank already, so that may not actually happen.

Diatoms won't be an issue, though. This tank is what I like to call a natural light tank, in that I don't have any daylight spectrum bulbs on it, so it lives off sunlight. IMO with other tanks in this exact position, I'm going to see only green algae, given the amount of sunlight it gets. And then, I'll be getting algae eating catfish (you know, ones that actually eat algae... not cories or plecos lol) and a mystery snail for cleanup. Quick google searches of apple snail sites say the true mystery species is extremely common all over Uruguay and Brazil where these fish are found, so it seems a perfect match. Plus mystery snails are really easy to source lol.

Great news! While typing out that novel above, I scrounged through my photos and found some somewhat clear pics of each gender.


This is the only female of the 5 I got. She's a great big sweetie lol. As you can see, she has no gravid spot. With her coloration, I don't expect to ever see one. Often white fish, or fish with white bellies, don't get a visible gravid spot. There's just enough opacity that it covers up the dark coloration. Anyway, she's the big one in the middle, the others are all boys. Please excuse their clamped fins - I'd just added them to the tank, so they weren't really settled in yet.


This is the largest male. He's only a tiny bit smaller than the female, but has a clearly developed gonopodium so he's definitely a he. I can only assume that with decent feeding and growing room, the males of this species aren't tiny, like you'd expect to see with guppies. They are incredibly non sexually dimporphic. It took a long time for me to determine that I had only one female, and I've been sexing livebearing fish for quite a while now.

The fish are more active every day, and beg for food whenever they see me in the kitchen. If I walk up to the tank, though, they all still swim to the back. I think it may take a few generations raised in captivity before they get totally domesticated.

Edit: I just realized I never updated. I was researching the catfish found in the area, as they are much easier to find information on, especially the cory species and oto flexilis, and as it turns out, Jenynsia Onca are most likely to be found in clear water that happens to have a low pH. So I'm building a blackwater tank without blackwater LOL.

[deranged chipmunk]

Very, very cool! Those are some beautiful fish. They are so different from the se Asia bettas.

I'm glad you posted this. It let's me get to be a fish geek again lol


Education is the most powerful weapon we can use to change the world ~ Nelson Mandela

[DigitalPunk]

Very cool! I have been doing some generalized research on planted tanks. Not sure If I will ever take the plunge and do a proper one, but have had fun with my limited exposure in a few of my Paludariums Thanks for sharing, those are beautiful fish and the tank is looking great!

[deranged chipmunk]

Ah, ya gotta at least do a low light tank Paul!! Some of my favorite tanks I ever did were high light, massive amounts of ferts and co2. The colors were spectacular. Maybe I'll have to set up a new one one of these days.


Education is the most powerful weapon we can use to change the world ~ Nelson Mandela

[Mentat]

Your biotope looks very nice . I tried my hand at a planted community tank and it was successful; maybe too much. Took me 1-1.5 hour a week to clean and water change a 65G with a foot long cichlid in it. My 26G bow front took 3-3.5 hours weekly to maintain and produced 1 gallon of plant trimmings too. It was nice, had Rosy Barbs and Tetras breeding in it; even with other fish, a few would survive and surprise me with their presence. Eventually decided to tear down due to all maintenance involved. Maybe one day will include a small water section inside a dart vivarium .

[junebug]

Your biotope looks very nice . I tried my hand at a planted community tank and it was successful; maybe too much. Took me 1-1.5 hour a week to clean and water change a 65G with a foot long cichlid in it. My 26G bow front took 3-3.5 hours weekly to maintain and produced 1 gallon of plant trimmings too. It was nice, had Rosy Barbs and Tetras breeding in it; even with other fish, a few would survive and surprise me with their presence. Eventually decided to tear down due to all maintenance involved. Maybe one day will include a small water section inside a dart vivarium .

This is why I love the walstad method. If done properly, you end up with a low light tank, no maintenance except water changesevery few months , and gorgeous colors in plants and fish. Which is why all of my tanks are walstad method lol.

[Mentat]

This is why I love the walstad method. If done properly, you end up with a low light tank, no maintenance except water changesevery few months , and gorgeous colors in plants and fish. Which is why all of my tanks are walstad method lol.

Thanks for info, first I read about it; will research and find out more .

[deranged chipmunk]

Oh Carlos, you gotta read Diane's book. It's a very interesting read.


Education is the most powerful weapon we can use to change the world ~ Nelson Mandela

[junebug]

I sent him the link to the El Natural forum on APC That way he can talk with her and other people who are better at this than I, lol.

I must get a video of these fish ramming each other. It's the oddest thing I've ever seen happen in a fish tank.

[junebug]

For those that like videos and aren't sick of this thread, yet:

YouTube