Rio Ucayali Biotope Project

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Seisage

Fish Crazy
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Dec 10, 2023
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Location
Pacific Northwest, USA
Background
So, I'm an ecologist and, more importantly, a pedant. I originally started out brainstorming for a 20gal long setup with the goal of having a nice, lush, heavily planted tank with fish that simply looked good together. This is a sane and normal way to plan a tank.

So anyway, I've decided to do a biotope tank featuring the Ucayali River of Peru.
Specifically, a small, shallow, slow-moving tributary of the Ucayali. This will be a log of my journey in setting up and maintaining this tank.

Tank
As mentioned, a good old classic 20 long! Thank you, man on FB marketplace who's downsizing and selling old tanks for $1/gal. I originally was going to go for a 20 high since I could get one for free, and I might still grab one (a free tank is a free tank, after all), but for this project, I think the greater horizontal space is going to be much better. Heating will be provided by two 50W Eheim Jager heaters. I'll be using sponge filters for that nice, gentle flow. Probably two of them, each rated for 20 gallons. Always nice to have more filtration capacity than needed. Does mean I'll have to get creative with scaping to hide them though. Sponge filters are great, but they aren't the prettiest things...

Abiotics (substrate, hardscape, chemistry)
In the slow-moving tributaries of the Ucayali, the substrate is basically exclusively fine, white sand. I could use CaribSea, but it's a little pricey and a bit coarse for the bottom-dwellers I plan to have. So, I'm going to go with pool filter sand instead. It's a little pricier than play sand, but with pool filter sand, I can get the light off-white color I'm looking for (and I hear it tends to be a little cleaner than play sand).

Of course, we can't forget the hallmark of slow-moving waters of the Amazon Basin... leaf litter! I'm hoping to collect a lot of this myself. I know a spot in the woods where there's always a really nice carpet of dead brown rhododendron leaves. To me, they look very tropical, especially when compared to deciduous leaves like oak. I've heard though that evergreens can be kind of iffy in terms of tank safety? Rhododendrons are in the Laurel family, so technically evergreen, but not conifers. If anyone has more information on this, I'd be happy to hear it. May also pick up a few indian almond leaves and other appropriate botanicals for better color.

Also hoping to collect a lot of my own driftwood for this. I'm lucky to live by the ocean, so we have an abundance of it. Of course, anything I collect will be boiled to hell and back, don't worry. I may still buy a couple pieces to replicate branches and small tree root structures, since most of our ocean driftwood is single chunks of smooth wood. Also planning on adding a couple pieces of really nice petrified wood I have laying around.

Lastly, I'm grateful to live in a place with very, very soft water. We don't have carbonate rock basically anywhere in my state, so the GH never gets above 50ppm. In my specific area, it's closer to 20ppm. Extremely lucky on this front. My tap water's pH sits pretty comfortably at 7.2, and I even found some old state-collected water quality data from 2013 that also put the water in my area at 7.2! Neat! I've tried to select for species that will tolerate this pH, although there's one (who shall be revealed later) that can't really handle pH above 7.0, so I'm going to see what the tank pH ends up being after the botanicals are added. They should bring it down enough, but if they don't, I have an alternative fish in mind that can handle up to 7.5.

Plants
So, as I'm sure many of you know, the whole deal with this type of ecosystem is leaf litter, leaf litter, and more leaf litter. Doesn't really leave a whole lot of room for plants in the substrate. Pictures of the substrate taken by Tom Christoffersen on his trip to the Ucayali back in 2009 show no live plants at all. That said... I'll probably plant one or two amazon swords (Echinodorus amazonicus) towards the back or side of the tank. I can just say we're right at the water's edge, how about that.

Although I don't have many options for rooted plants, I get to go crazy wild with floaters! The Ucayali apparently regularly has two or more species of floating plants coexisting, which I understand is somewhat uncommon in a lot of areas. I'll be primarily using water lettuce (Pistia stratiotes) and amazon frogbit (Limnobium laevigatum). These are nice, fast growers and will be great for silent cycling the tank, I think. At some point, I'll probably try to corral them with floating rings if I can find or make some, just to let a bit of light into the tank.

Livestock
Oh boy, here we go. Researching livestock is really what led me down the rabbithole of biotope aquariums. Here are my eventual plans for a completed tank:

1x Apistogramma agassizii (this is the pH guy... Will substitute a cacatuoides if I can't get the tank pH low enough with botanicals)
8x Neon tetra (Paracheirodon innesi)
6x Marbled hatchetfish (Carnegiella strigata)
4x Zebra oto (Otocinclus cocama)
Inverts?? (please advise)

This stocking level is listed as 76% on AqAdvisor, and since I'll be letting the tank adjust with multiple small additions of fish, I think I feel comfortable with this level. That said, this tank won't be very heavily planted, so I may add or substract depending on how my tank responds and how much I feel it can handle. I am seeking advice on stocking order though. Would it be better to get the apisto first so it has a chance to settle in and claim a territory, or would the fact that it'd be the first fish in the tank make it a bit feistier with the subsequent tankmates? I know apistos aren't known to be especially aggressive, and since I'm not planning on getting a pair (so no brooding), I don't think it'll ultimately be much of an issue, but I'll look into it more. I was planning on getting the apisto last, mostly since I want the tank to be mature and stable beforehand, but I can change that if need be. To my knowledge, it should be fine with the otos given plenty of hiding spaces. Another reason why a 20 long is better, for more floor space.

The inverts I'm a little stumped on. I think it would be great to have a couple snails or shrimp as a CUC, but in trying to stick with the biological accuracy, I would want inverts ideally native to the Ucayali, or at least the upper Amazon Basin. However, I've heard that there are basically no Amazonian inverts available in the hobby... Is this true? I haven't been able to find any for sale myself, but maybe one of you has more knowledge on this.

---

Well, that's basically my entire current plan laid out, I think! I'm very excited for this tank. I definitely wanted an Amazon community tank, but felt unfulfilled by the idea of a pan-Amazonian look or the typical Rio Negro biotope.

If anyone has any tips or advice, they will be very welcome. I'll keep this journal updated as I start collecting hardware and putting this whole thing together.
 
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Well, I've collected some wood over the past couple days! Most of it salvaged from a local beach as driftwood, some collected as dead sticks in the woods. I'm fairly sure none of it is conifer, or if it is, it's weathered enough to have lost its terpenes, resins, etc. I did my best to find hardwood and test each piece I collected. It's a bit difficult to identify soft vs hard woods in their natural states. Most resources online only tell you how to differentiate the two when it comes to lumber products. However, a couple of the very weathered pieces do have strong grain patterns, which is a good sign.

I did try the fingernail test, but I feel that it's somewhat unreliable. I was able to make fingernail marks in every single piece of wood, even those from known hardwoods like madrone. That said, the pieces shown in the picture here required much more effort to mark than others, where I could gouge into the wood with minimal effort, so I feel comfortable that these pieces will last an acceptable amount of time in the tank.

Some of them definitely still need bark removed, but that will have to wait until after I'm done traveling. If the bark proves stubborn, I may soak them for a little while. I definitely won't be soaking all of them though, as I absolutely want the tannins for this tank. Everyone will get a nice good scrub (one piece of driftwood actually has a tiny barnacle on it!!) and have boiling water poured over them to kill any nasties living on the surface.

Depending on how the cleaning process goes and how well they fit into the eventual scape plan, I may still buy a couple pieces of aquarium wood from a LPS. They'll probably end up being longer-lasting, and things like spiderwood have a lot more little branching bits for hiding spots than my collected wood has. We'll see how it all fits together when I have the tank in my hands.

p.s. don't take foraged wood into your home if you can help it 😂 The number of little bark bits on my floors is staggering. Unfortunately, I live in a very damp place, so wood left outside would never dry. And, honestly, it may get stolen. People around here are weird.
 

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Wow good luck! I personally could never have the patience to do a biotope tank because of all the other fish I would want to keep in the tank, but good on you for trying.

I think that your plans with the floaters could do with something like a stick-corral, like a corner of the tank where the wood reaches the surface and kinda makes some kind of weak barrier to keep your floaters in. It's a little prettier than plastic and doesn't require constant adjustment.

As for the shrimp, even if you find a species that is native to the river, for such a small tank the apistogramma might wipe out the colony, or scare them so much they never leave the corners and you never see them.

If you want hatchetfish maybe consider a good lid because those are known to be jumpers. I personally haven't kept them but I had been considering them and read that they are avid jumpers and need lids.

Other than that good luck!
 
Wow good luck! I personally could never have the patience to do a biotope tank because of all the other fish I would want to keep in the tank, but good on you for trying.

I think that your plans with the floaters could do with something like a stick-corral, like a corner of the tank where the wood reaches the surface and kinda makes some kind of weak barrier to keep your floaters in. It's a little prettier than plastic and doesn't require constant adjustment.

As for the shrimp, even if you find a species that is native to the river, for such a small tank the apistogramma might wipe out the colony, or scare them so much they never leave the corners and you never see them.

If you want hatchetfish maybe consider a good lid because those are known to be jumpers. I personally haven't kept them but I had been considering them and read that they are avid jumpers and need lids.

Other than that good luck!
Thank you!! And yes, I absolutely want to keep other kinds of fish. The solution to that, of course, is getting more tanks 😂

That's a good idea for the floaters, I'll have to try that. And I did have that thought about the Apisto and shrimp... Hopefully I can find a snail species, but I have a feeling it's unlikely. Oh well. And yes, I will 100% be putting a lid on the tank haha. Just bought one today, actually! It'll help keep evaporation down anyway until I can get the hatchetfish.

p.s. love your signature lol
 
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I am hoping you are having a lid on this tank, for the hatchetfish :) they are reaaaaally good jumpers. Like 0,5cm gap and they are gone. Also they need areas with open water surface and calm parts while they also need the floating plants but not too many. They wont stray from the surface level not even 1 cm below, and they do not swim under plants in my experience. I have Carnegiella marthae so maybe the marble one will be a bit different, but knowing what I know now, I would never ever get them again :) also nigtmare to feed, I am super confused how they didnt starve yet.

In the stocking order, I would go neons+hatchetfish, wait a month, add the apistos, wait three more months, add the otos/possible shrimp.

I never had apistos (not yet anyway) but if they are something like my bolivian rams, they will kill all the ramshorn snails, all the snails that dare to approach tehir territory, they will poke at the nerites and I would not risk anything with long eye stalks with them (like mystery snails, rabbits,...) You can get a nice colony of ramshorns, they are the easiest to get rid of eventually and they take some months to start really breeding. I also like them way better than the usual bladder snails in terms of appearance. There is just something in the hemoglobin

I am glad you are not considering corydoras, as they should not be kept with apistos, not in the smaller sizes anyways. I do not like the neon tetras, but that is just my preference

Good plan, fingers crossed!
 
I am hoping you are having a lid on this tank, for the hatchetfish :) they are reaaaaally good jumpers. Like 0,5cm gap and they are gone. Also they need areas with open water surface and calm parts while they also need the floating plants but not too many. They wont stray from the surface level not even 1 cm below, and they do not swim under plants in my experience. I have Carnegiella marthae so maybe the marble one will be a bit different, but knowing what I know now, I would never ever get them again :) also nigtmare to feed, I am super confused how they didnt starve yet.

In the stocking order, I would go neons+hatchetfish, wait a month, add the apistos, wait three more months, add the otos/possible shrimp.

I never had apistos (not yet anyway) but if they are something like my bolivian rams, they will kill all the ramshorn snails, all the snails that dare to approach tehir territory, they will poke at the nerites and I would not risk anything with long eye stalks with them (like mystery snails, rabbits,...) You can get a nice colony of ramshorns, they are the easiest to get rid of eventually and they take some months to start really breeding. I also like them way better than the usual bladder snails in terms of appearance. There is just something in the hemoglobin

I am glad you are not considering corydoras, as they should not be kept with apistos, not in the smaller sizes anyways. I do not like the neon tetras, but that is just my preference

Good plan, fingers crossed!
Absolutely yes to the lid. I actually mentioned in my previous post that I just bought one! Good to know to look out for even the tiniest of gaps. I did actually get a chance to go to a not-so-local fish store yesterday!! It’s a 2.5 hour drive from where I live, but it beats having to ship fish in. But I got to see the marbleds in person for the first time there! They were soooooo tiny. Just juveniles, of course. But definitely drives home the point that I’ll need a reeaaalllly well-fitting lid 😬
Regarding surface access, yes, that’s why I’m planning on having a way to corral the floaters, and I’ll be using sponge filters with air stones, so the water disturbance should be minimal.

Thanks for the stocking order input! That’s what I had in mind, so good to know my intuition was correct.

And yes, I very quickly learned through my research that corys would NOT be a good fit with the apisto haha. That’s alright with me, I like the look of otos better anyway. Regarding the neons, I think they’re beautiful, but if it were up to me, I’d probably pick cardinals instead and just choose a different river system for the biotope… The thing keeping me from cardinals is that I have a lone neon that I adopted from an acquaintance and from what I understand, neons and cardinals don’t really school together 😞
 
Went SCUBA diving a couple days ago in a local rock quarry and got a chance to pick up a few nice pieces of wood from the bottom.

Sadly, it’s not the really nice preserved stuff. A good chunk of my haul was simply rotting wood… I do have a few keepers though. A really lovely piece of unknown hardwood that has some very pretty old worm tracks on the surface. Also a few nice birch branches that have some really good coloration. There are a couple others that are iffy. Still a bit soft, but I want to give them a chance to dry a bit and then reassess.

I was really sad about this one extremely nice large weathered hunk. Unfortunately, as I started scraping away the top layer of gunk, I quickly realized that the wood was just too soft all the way through… Wouldn’t have lasted long in an aquarium. My scraping also revealed small red worms burrowed in the wood. Not sure what they are, but I probably don’t want them in my tank lol. Might post a picture of the keeper pieces at some point.

Edit: actually, I’m wondering if the worms might be bloodworms (midgefly larvae). Do they burrow into old logs? I suppose they wouldn’t be the worst to have in a tank after all (free fish food!) but the wood rotting quickly would still be an issue anyway.
 
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Some advice from my own attempts...
Pistia won't grow with a lid. It needs sunlight to thrive, and open tanks. Hatchets (I love hatchets) and open don't mix.

I have been contemplating a hatchet tank, also for strigata. I can't find them locally. But they are best kept in tanks high off the ground, or beside a favourite chair. They cling to the surface, and with a standard stand, you don't see them. It helps if you can somehow look up.

A 20 long is a wonderful shape for such a tank, but surface hatchets expect more warmth and sunlight than undergrowth tetras.

I used to breed agas, and soft water is needed. pH never seemed to matter. My tap then was 7.4, and they lived long, non breeding lives in it. There was a huge difference in what they needed to live, and what they needed to live more than one generation. Also, in the hobby now, 'unmodified' agas are hard to find. There are a lot of linebred fish out there.

I also used to breed a lot of Apistogramma njisseni, caught wild at pH 5.5. They would successfully breed at 6.6 to 6.8, as long as the mineral hardness was very low. I'm a little dismissive of pH as a useful indicator. In my experience, hardness is everything. I can breed cardinals at pH 6.5.

A lot of leaf litter calls for vigilance. Leaf litter tanks need constant checks, as if the parasite Oodinium is present, it thrives in decaying leaves and acidity, and can be a serious fish killer. I use oak, and change it out regularly. You have to watch out who you're creating a habitat for. I've learned that the hard way.

Check out below water.com for wild videos, as well as Ivan Mikolji's site. They're fun.
 
As for a cover for the hatchets, you can buy a screen repair kit and cut the frame to size. Aluminum cuts easily with any normal power saw (wear safety goggles) or hand hacksaw. Use 3/8" square bird netting instead of screen. It will allow most light through and no chance they are going to dive through a 3/8" square. They do make 1/4" mesh if you really are worried. One roll is enough to make more covers than you'll ever need, so you can go in business if you'd like.
 
Some advice from my own attempts...
Pistia won't grow with a lid. It needs sunlight to thrive, and open tanks. Hatchets (I love hatchets) and open don't mix.

I have been contemplating a hatchet tank, also for strigata. I can't find them locally. But they are best kept in tanks high off the ground, or beside a favourite chair. They cling to the surface, and with a standard stand, you don't see them. It helps if you can somehow look up.

A 20 long is a wonderful shape for such a tank, but surface hatchets expect more warmth and sunlight than undergrowth tetras.

I used to breed agas, and soft water is needed. pH never seemed to matter. My tap then was 7.4, and they lived long, non breeding lives in it. There was a huge difference in what they needed to live, and what they needed to live more than one generation. Also, in the hobby now, 'unmodified' agas are hard to find. There are a lot of linebred fish out there.

I also used to breed a lot of Apistogramma njisseni, caught wild at pH 5.5. They would successfully breed at 6.6 to 6.8, as long as the mineral hardness was very low. I'm a little dismissive of pH as a useful indicator. In my experience, hardness is everything. I can breed cardinals at pH 6.5.

A lot of leaf litter calls for vigilance. Leaf litter tanks need constant checks, as if the parasite Oodinium is present, it thrives in decaying leaves and acidity, and can be a serious fish killer. I use oak, and change it out regularly. You have to watch out who you're creating a habitat for. I've learned that the hard way.

Check out below water.com for wild videos, as well as Ivan Mikolji's site. They're fun.
Wow, somehow I missed this response. Thanks for your insights, Gary! The lid I have is a glass one, which will let plenty of light through. I have indeed heard that pistia doesn't do well with closed tanks, but I did see some thriving under glass lids at an lfs I went to while visiting family recently, so I'll take my chances with it and if it doesn't do well with the glass lid, I'll reassess and maybe find a mesh one.

It appears I never ended up mentioning this in this journal thread, but the tank I'll be using will actually be a 25gal! It's a bit of an odd one in that it's basically just a taller 20g long, which is actually fantastic for this project as it has the same footprint, but gives a bit more vertical space for each of the fishes to stratify out into their preferred zones.

I'm so happy to hear that agas can do well at slightly higher pH. My water sits at 7.2 pretty consistently. I expect acids from wood will bring it down slightly, but I don't want to count on that. I don't plan on trying to breed, so that's not a concern to me. I bought API's liquid GH/KH test kit since my water provider doesn't give numbers on their website and as suspected, I am blessed (or maybe cursed, depending on how you look at it) with very soft water like you are. GH and KH are both 35ppm straight from the tap. Granted, I didn't let the water sit overnight, so maybe the true values are slightly different. My 5gal tank's water is ~50ppm GH and 18ppm KH. Not sure what's bumping up the GH in there, but it's still soft water.

Good advice re: leaf litter, thank you👍
 
Other general project update. I'm home from traveling, so this tank's setup can finally continue! I fully cleaned out the tank I'll be using last night. As mentioned in my previous post, it's a 25gal instead of a 20, which I'm quite excited about.

I'm always very bad at remembering to take "before" photos of my cleaning projects, so unfortunately I can't show the transformation, so you'll just have to take my word that the tank was very, very grimy. The plastic rims are also a bit scratched up and not the prettiest, and the glue in them was old and brittle, so I had to scrape it out along with all the other dirt and grime that had collected in them. The result is that the rims are not firmly attached to the tank, which I don't think will really be an issue. Might re-glue them in the future, we'll see.

But the best news is that it holds water!! I completely filled it and marked the water level before leaving for my 2-week trip and there was no dampness at the seams when I got back. The water level had decreased ever so slightly, but considering the seam integrity, it had to have just been evaporation. My substrate just got in, so hopefully I'll be able to post another setup update later on today.
 
As to the lid issue, you can get 1/4"-3/8" bird netting and an aluminum window screen kit to make a very nice "lid" that will keep jumpers out. Just use the netting instead of the screen it comes with. It let's almost 100% of the light and air circulation through.
 
As to the lid issue, you can get 1/4"-3/8" bird netting and an aluminum window screen kit to make a very nice "lid" that will keep jumpers out. Just use the netting instead of the screen it comes with. It let's almost 100% of the light and air circulation through.
This might be the way I have to go, considering the glass lid I bought doesn't actually fit. The width measurement written on the box is 1" longer than the actual thing, so there's a 1" gap at the top of the tank 😒

The screen frame kit is a good idea though. And thankfully they aren't too expensive.
 
I have 3 silver hatchet fish. I've read they jump less than the others. I bought 5 from AquaHuna. They all arrived alive, but one was missing after a couple of days. I have very small openings around where my filter hoses go in and out, but I've read they are very accurate jumpers. I can only assume one jumped out and the cats got him. A couple of weeks later, another died mysteriously. The other 3, however, have thrived and I LOVE them. They have nice patterns of darker colors on their bodies and they are so fun to watch. I haven't seen them try to jump at all and I have my lids open or off quite a bit while I change water, trim plants, etc.

I think the marble hatchets jump a lot more, though, so the caution recommended is probably better than my cavalier approach.

BTW, I had to look up the word "pedant." LOL - it fits. :D

I looked up the Ucayali River and found a video of a biotope tank. Leaves, Leaves, Leaves!!! This one had no live plants at all- just dead leaves and branches. That look is not my cup of tea, but I love the idea of having a slice of a specific place in the tank- hat's off to you!

It's been said already, but I would leave the otos for last. Honestly, all the fish you're getting need really clean water I think, but your parameters look like you will pretty much have it out of the gate. It's just hard to say what would be best to add first. Maybe start with the cheapest fish- neons, I reckon.

I've read that over-filtering for black water fish is really key- for me it's like insurance anyway- looks like you're doing that. The article I linked to is worth a read and there's an interesting dive into a blackwater biotope as well. A pedant might very well be interested in reading :cool::cool:

Can't wait to see how it goes!!!
 
I have 3 silver hatchet fish. I've read they jump less than the others. I bought 5 from AquaHuna. They all arrived alive, but one was missing after a couple of days. I have very small openings around where my filter hoses go in and out, but I've read they are very accurate jumpers. I can only assume one jumped out and the cats got him. A couple of weeks later, another died mysteriously. The other 3, however, have thrived and I LOVE them. They have nice patterns of darker colors on their bodies and they are so fun to watch. I haven't seen them try to jump at all and I have my lids open or off quite a bit while I change water, trim plants, etc.

I think the marble hatchets jump a lot more, though, so the caution recommended is probably better than my cavalier approach.

BTW, I had to look up the word "pedant." LOL - it fits. :D

I looked up the Ucayali River and found a video of a biotope tank. Leaves, Leaves, Leaves!!! This one had no live plants at all- just dead leaves and branches. That look is not my cup of tea, but I love the idea of having a slice of a specific place in the tank- hat's off to you!

It's been said already, but I would leave the otos for last. Honestly, all the fish you're getting need really clean water I think, but your parameters look like you will pretty much have it out of the gate. It's just hard to say what would be best to add first. Maybe start with the cheapest fish- neons, I reckon.

I've read that over-filtering for black water fish is really key- for me it's like insurance anyway- looks like you're doing that. The article I linked to is worth a read and there's an interesting dive into a blackwater biotope as well. A pedant might very well be interested in reading :cool::cool:

Can't wait to see how it goes!!!
Thank you! I'm very excited about it myself. I do think the screen mesh lid will be best for the hatchets. I'll get the very fine bug netting type and won't even cut holes out for hoses and such. I'll just punch them through the mesh so it's a super snug fit with no gaps. I do think I'll be adding the neons first. They are indeed the cheapest and it'll give me more time to make the custom lid and let the tank continue to mature for the more sensitive species.

I will definitely have live plants though! I'm also not a huge fan of the bare sticks and leaves look. The Ucayali basically only has floaters, but it has quite a lot of them. I actually just got some frogbit yesterday. It's currently imprisoned in a bowl of water on my countertop until I finish getting the tank set up lol
 

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