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Rio Orinoco biotope questions

ButchAZ

New Member
I see lots of biotope tanks with plants in them. It's my understanding from what I'm reading that the blackwater areas of the Rio Orinoco watershed are mainly free of aquatic plants. Are folks just taking artistic license, or am I missing something??

For those with planted blackwater tanks, are you running CO2 injection?

Thanks!
 

Mike Wise

Moderator
Staff member
5 Year Member
Artistic license is my guess. Every blackwater biotope I've seen (in Peru & Colombia) had submerged terrestrial grasses along the shore and some emergent bog plants. Other than that, only algae coating branches. Here's a picture of an intrepid explorer (Tom C) checking out a blackwater stream near Leticia, Colombia.
upload_2018-9-19_10-36-34.png
 

dw1305

Well-Known Member
5 Year Member
Hi all,
I see lots of biotope tanks with plants in them. It's my understanding from what I'm reading that the blackwater areas of the Rio Orinoco watershed are mainly free of aquatic plants. Are folks just taking artistic license, or am I missing something??
Yes and no, they don't have water plants in quite the same way that a European or North American river might, but they are may have floating plants, like Water Lettuce (Pistia stratiotes), if there is enough light.

Fish are collected at lower water when the forest is dry and fish are restricted to small water bodies, often choked with leaves and fallen wood, but when the rainy season comes the forest floor will flood and the fish will disperse through the flooded forest. An appropriate biotope would consist of silica sand (blackwater streams flow across base poor substrates), covered in structural leaf litter and twigs, with a surface layer of floating plants and emergent palms and aroids etc.

If you look at TomC's travelogue pages from the W. Amazon basin in Peru you can see the <"types of water body"> where they collected Apistogramma from.
For those with planted blackwater tanks, are you running CO2 injection?
No even if you have submerged plants, they can only make use of additional CO2 if other nutrients are available. Black-water has virtually no ions, of any description, in it.

Additionally the pH depression you get from CO2 addition is slightly different from the pH reduction you get from humic and tannic substances.

cheers Darrel
 

Tom C

Well-Known Member
5 Year Member
The waters of Orinoco and the Colombian Rio Negro mostly look like this:





Some of these places we could find the amazing miniature chameleon-tetra Ammocryptocharax elegans. When it lies on a plant leaf, it is completely green. When scared, it immediately turns brown spotted, like here:



The green in the water is usually not waterplants:





Here we collected Apistogramma diplotaenia:







and here I collected 11 Apistogramma diplotaenia before breakfast:





Going up small blackwater streams



we some places spotted a little green below the surface:





This one just jumped up into the boat:



These look more like water plants than terrestrial plants, to me:



and there were also plants that looked very much like waterplants!
In water with a pH of more or less 4, and a conductivity of less than 10 microSiemens/cm!

 

ButchAZ

New Member
Wow Tom, thanks!! Those are GREAT photos! That one little guy looks pretty vicious. Do you know what species that is? Looks like a barracuda.

Those will be helpful for my next tank!
 

dw1305

Well-Known Member
5 Year Member
Hi all,
Wow Tom, thanks!! Those are GREAT photos! That one little guy looks pretty vicious. Do you know what species that is?
They certainly are great photos.

The fine leaved plant, in the last photo, looks like Mayaca fluviatilis, the grassy leaved plant may be a grass, but there is no real way of telling.

The plant with the bifid leaf below (and the plant at the top of the photo), are seedling palms (Arecaceae), and the grassy leaved plant looks like it may be a Sedge (Carex sp.), but that would be guess-work.



Some-one will do the exact species of "toothy" fish, but it is a "Dog Characin", something like <"Acestrorhynchus falcatus">.

cheers Darrel
 

gerald

Well-Known Member
5 Year Member
I've seen Mayaca (the feathery plant in Tom's last photo) a few times in the Sandhills region of North Carolina, in low-conductivity blackwater stream habitats that look pretty similar to Tom's photos. But it was rooted in organic-rich sandy mud near the stream bank, not in plain sand. The grassy-looking plants could be true grasses, sedges, pipeworts, rushes, pondweeds ... lots of possibilities. Here's a pondweed (Potamogeton) from a blackwater creek in Hope Mills, NC that I first thought was a grass. Water was very low at the time and this part of the stream bed was exposed.
 

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