Blackwater themed aquarium

[MitchM]

As it turns out, the Amazon River basin is not what I thought it was.

I have always thought that the Amazon River basin was a nutrient rich environment where there was no shortage of nutrients for all types of organisms to live and thrive. As it turns out, the dense forests that we typically see are the extent of the nutrients available. What that means is that the nutrient cycle is so efficient that most organic matter in the forest is recycled back into the forest within minutes, not hours, days or months. For example, monkey dung that lands on the forest floor is consumed and broken down into it's chemical elements well within 1 hour, ready to be taken back up by the plants in the forest.

This leaves very little nutrients available to be washed down into the river systems.
As a result, Amazon rivers are fairly clean, sterile environments, void of plants and where the majority of fish are carnivores.
Cardinal Tetra gut content analysis has shown these fish to be carnivores. From my experience, we aquarists seem to view all fish as omnivores, that they can be fed whatever is available and that is fine. If we truly care about the fish we keep, I think we should be feeding them the foods that they have evolved over time to consume.

Add to this the fact that the Amazon River basin receives approximately 40 million tons annually of mineral dust from Lake Chad in Africa!
http://iopscience.iop.org/article/10.1088/1748-9326/1/1/014005/pdf

All this makes creates a very interesting environment that I want to learn more about, so I'm making my 600g aquarium into a blackwater themed aquarium. Of course I can't recreate the exact similar conditions, so I'm working within the limitations of an enclosed aquatic ecosystem as best I can.

This won't be an aquarium focused on aesthetics, hopefully it will be a balance between aesthetics and functionality.

 

[MitchM]

I'm focusing on the Rio Negro in Brazil. https://en.wikipedia.org/wiki/Rio_Negro_(Amazon)
The water conditions vary between:
PH less than 5 to 7
Conductivity approximately 10 ppm
High DOC content (mainly in the form of tannins and humid acids)
Nitrates 7 - 20 ppm
Water temperature 28c/82f

Currently, my aquarium parameters are:
PH 6.5 without aeration/7.6 with aeration
Conductivity 125 ppm
DOC no method to measure, but there are long lasting bubbles on the water surface with aeration ( a good sign of high DOC)
Nitrates 1
Temperature 27c/80f

I have a ways to go to eventually reach some target parameters, but because I am using a garden soil/amazon soil substrate, I may not be able to bring the TDS down far enough. Minerals in the substrate may just keep on dissolving with a low PH which will keep the TDS levels elevated.
Water circulation is important, but I have a leaf litter on top of substrate base that will be disturbed with any substantial water flow.
An external filter is not a good idea because it operates on the basis of water movement keeping detritus suspended until the detritus can be mechanically separated and removed. I am going to go with a trickle water change method with reverse osmosis water.

I am using a soil substrate so I can have plants that will feed off of settled detritus and prevent a buildup of phosphate and nitrate.
It's a little difficult to photograph an 8' long aquarium.

 

[sissy]

To me a novice to this sounds like you are looking to warm up your cold winters with something inside .I have a big tank and it is empty in the basement and sometimes used for sick smaller fish but it is in front of the basement window so it is easier to maintain stock tanks

 

[MitchM]

To me a novice to this sounds like you are looking to warm up your cold winters with something inside ....

Actually I'm starting this project now because I know I'll be having the covers off the aquarium quite a bit and I didn't want to deal with all that extra indoor humidity during the winter.

 

[Meyer Jordan]

I am using a soil substrate so I can have plants that will feed off of settled detritus and prevent a buildup of phosphate and nitrate.

I seem to remember reading somewhere that the Rio Negro did not have any sediment substrate at all. That this was also one of the largest differences between it and the Amazon river. The bottom of Rio Negro was bare shale. Or am I confused?!

 

[MitchM]

This is some of the leaf litter I'm adding to the aquarium to provide humid substances.
Some almond leaves are 12" in length, some seed pods are 10".

 

[Lisak1]

That looks like it would be very pretty in a bowl of potpourri!

 

[sissy]

I thought the same when I saw it lisak1

 

[MitchM]

I seem to remember reading somewhere that the Rio Negro did not have any sediment substrate at all. That this was also one of the largest differences between it and the Amazon river. The bottom of Rio Negro was bare shale. Or am I confused?!

The river basin transitions from finer sediments, minerals and sand to mainly sand along the basin pathway.

http://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_6/b_fdi_45-46/010009753.pdf

I'm still learning about it but I wanted to set up a system that could absorb the detritus I knew was going to accumulate and have a method of exporting the nutrients out of the system.

I could not come up with a solution for recreating a river bottom that could work long term.

 

[MitchM]

That looks like it would be very pretty in a bowl of potpourri!

I thought the same when I saw it lisak1

potpourri...

 

[MitchM]

After an initial boiling and rinsing of the leaves and seed pods, they were placed in the aquarium and after a couple of weeks became covered in fungus as part of the decomposition process. I have aeration going so as not to allow the O2 levels to drop too low. 2 weeks of being covered in fungus the leaves are clean and decomposing further. You can see right through some almond leaves now.
I guess the leaves are going to have to be replaced on a regular basis.

 

[DutchMuch]

I wouldn't change out the leaves, just watch your phosphates & nitrates.

 

[MitchM]

I wasn't planning on changing them out, just adding more as the current ones completely decomposed.
I'm going to start out with a fairly low reverse osmosis trickle water change rate and adjust it as the nitrate numbers dictate.

 

[DutchMuch]

ah ok you said replace I thought you meant take the old out and put in the new, yea definitely add more leaves and cones, seed pods etc as time goes. get some amano shrimp to, or cherrys, they will love that biofilm. Just make sure you drip acclimate if you do get some of them. Idk if they are native but for a ground cover fish corydoras sp. is a good fish for your tank to. Just some recommendations lol

 

[MitchM]

Thanks. I have about 60 corydoras adolfoi in another tank I will be adding as soon as I can catch them.