Blackwater tank 80cm

[LMuhlen]

Having just assembled my new tank, which was hanging for a long while in my thoughts, I thought I'd keep track of things here and hopefully get some suggestions. It is not really a planted tank, but floaters are expected, and maybe a crypt here and there.

The idea was to make a black water, high temperature tank. In secret, this is a learning experience for my dream of having a wild discus tank, which may eventually come true some years from now.

Original plan is to have lots of wood, some rounded stones, white sandy substrate and lots of decaying leaves.

Fish wise, I want green neons, so I'm looking for other tiny fishes to go with them. For now the plan is as follows:
~15 green neons (Paracheirodon simulans)
~10 Tucan tetras (Tucanoichthys tucano)
~6 Morpho tetras (Poecilocharax weitzmani)
~7 Corydoras Nijsseni
~ Some kind of otocinclus or paratocinclus?

Morpho tetras could be replaced by checkerboard cichlids. Discussing fauna here.

The tank is 80 x 30 x 35cm, 84L, with glass lids.
Filtration is a HMF with a 500L/h pump, reduced to ~300L/h. In order to avoid any kind of apparent water currents, I discharged the water in another thinner HMF on the opposite corner. This worked great, the water looks absolutely stagnant, even though there is decent circulation through the filter. On the pump side, I added an air stone to boost aeration. The pump grabs a few bubbles and atomizes them, but all bubbles are hidden behind the foam sheets.

I'll keep the heater in the discharge HMF and the probe in the main HMF. Expecting to keep temperature between 27 and 28ºC, which isn't hard most of the year around here, but it may increase uncontrollably during heat waves...

I wanted weak lighting, and I seriously hope not to have any kind of algae issues in this tank, even if I need to use ambient light only eventually. But I got a simple light at a discounted price, and it is a little brighter than I planned. For now, I covered it in paper towel to reduce the brightness and make it more diffuse, but I'm considering using a dimmer. I would need to cut the wire after the power source and install plugs, so I'm thinking this through as I have never tried this.

I found some really pretty twisted vines in a shop specialized in dried flowers for decoration. They were almost 4m long and basically free. I got one and sawed it into pieces, improvising the positioning as I went. I never used anything like this, and it was impossible to boil or anything like that due to the size, so I'll see what happens. So far, I can say that it made the water really dark in only 12h. I got the tip from a fellow aquarist who used them in a very pretty and successful discus tank, so I'm hopeful it will be safe. They are still trying to float, but given the size it was pretty easy to keep them in place.

I collected a few assorted leaves, this part is very new to me, so I'll have to go trial and error. Most of the recommendations I see are from trees unavailable down here, but we have a lot of diversity. If only I knew anything about trees... So far I added only a few, but the idea is to add many more. I have very easy access to catappa leaves, they are everywhere, but I think they are too large. So far I hid one leaf inside the filter, and I may cut some into smaller forms eventually.

The water dawned a little milky other than very dark. I'll keep things rolling for a while and eventually do a big water change.

 

[Mike Singh]

Do you need some more open space in the front for the Corys to rummage around, else you’ll never see them?

 

[Bradders]

Fish wise, I want green neons, so I'm looking for other tiny fishes to go with them. For now the plan is as follows:
~15 green neons (Paracheirodon simulans)
~10 Tucan tetras (Tucanoichthys tucano)
~6 Morpho tetras (Poecilocharax weitzmani)
~7 Corydoras Nijsseni
~ Some kind of otocinclus or paratocinclus?

Morpho tetras could be replaced by checkerboard cichlids. Discussing fauna here.

That is going to be quite a community of fish!

The Checkerboards can grow up to 3 inches or so, so that is going to be the largest water column fish I think?

 

[LMuhlen]

Do you need some more open space in the front for the Corys to rummage around, else you’ll never see them?

I hadn't thought about that, but it makes sense. At this point, moving the larger stones would be too much trouble, especially if I wanted to keep the polystyrene under them. But I could very easily move the smaller stones and open up space. I can also avoid having leaf litter at the front right side of the tank and stack it in the back. When I get there, I'll see what the cories decide to do and react accordingly. But in the end, not seeing them all that much wouldn't be so bad, they could be like a little surprise that pops up every now and then.

That is going to be quite a community of fish!

The Checkerboards can grow up to 3 inches or so, so that is going to be the largest water column fish I think?

From what I saw, the filamentosus is less than 4cm long, neglecting the tail. The maculatus is maybe 6cm? But I'd probably look for filamentosus. Still, they are plan B after the morpho tetra. The water being dark and with all the leaf litter, I imagine only the neons popping up, with the darker tukanos being more discrete, and the rest being mostly hidden.

 

[John q]

From what I saw, the filamentosus is less than 4cm

My male is about 70mm and the female about 50mm. They will vary in size but are definitely bigger than 40mm.
Had them around 12 months, so assuming the are fully grown.

 

[Jorge O'Reilly]

My male is about 70mm and the female about 50mm. They will vary in size but are definitely bigger than 40mm.
Had them around 12 months, so assuming the are fully grown.
View attachment 216960

That right there is my next fish. Gorgeous. I'd ditch other species if necessary in order to make it fit IMO.

 

[LMuhlen]

It's been 3 days and the water has turned very dark very fast. It looks like cinnamon tea. It's not as cloudy as it was, but it's hard to tell for sure. My plan is to leave the tank alone for at least a week before changing any water. I would be very interested to see what happens to the fishes appearance and behavior in such a dark water, but I'm guessing that it will clear a bit by the time it is fish ready. I didn't add nearly as many leaves as I was planning, so I'm guessing this red color is mostly from the wood pieces.

On the side of the filter where the air bubbles have passed through the pump, a thick foam is forming that stains the glass brown. I think it may be happening something similar to salt water skimmers, although I'm completely clueless when it comes to salt water stuff. I'm removing it with a spoon every now and then.

One floating plant added to see how it goes. It will only get ambient light for now.

Overall, I'm very excited about this project, I hope that nothing that I'm using turns out to be toxic or anything like that.

 

[LMuhlen]

People talk about their water being liquid rock, well, this tank turned into liquid wood. It got to the point where I can't see more than 5cm deep.

I had an empty ~35L tank that I recently dismantled, and with the excuse of not letting the silicone dry I filled it with water next to this tank and I'll use it to help with water changes. So I added some of the same dried leaves in it, thinking that this will help prepare water for WCs, set it with a small filter to keep water moving and at some point I may add heating, but right now we are struggling through a heat wave. The fact is that the water didn't change color in a noticeable way. I conclude, therefore, that it is the wood pieces doing all this to the water.

Today I changed 28L of water, which will probably be my standard water change, just to test it. As expected, this didn't change the color one bit. I'll probably have to do some 90% changes to get things going. Right now I can't even test for ammonia or pH with so much pigment in the water. I'm afraid it will also stain my clothes.

On other news, the tank is releasing a very pleasant smell. A bit floral, kind of sweet. I'm tempted to drink a little bit haha. The side tank also smells nice, so it must be the leaves.

I tested TDS with my cheap pen. My tap water gives ~80ppm, the side tank with the leaves is at roughly 90ppm and this tank is at ~160ppm. I didn't expect the tannins and whatnot to affect TDS. It could be the sand, which was once used in another tank and left in storage dried for more than an year. I just rinsed it a few times, so there could be something that leaked from it. The sand itself should be inert. Maybe the stones? I used similar stones in my other tank and they look inert as well.

 

[LMuhlen]

A day or two after the last post, I couldn't take it anymore and I did a near 100% WC. I just changed as much water as the siphon removed without digging a hole on the sand. Surprisingly, as I filled the tank back up, the water was painted back immediately. The remnants of water and the stain on the glass was enough to make it black water again. So far I have done 5 complete water changes and it looks like now it is close to a good place regarding the rate of darkening. The thick brown foam that was forming where the bubbles from the airstone were crushed by the pump are no longer forming.

Unfortunately, around WC number 2, that typical white goo started forming around the wood pieces. I'm not sure if it because of the amount of wood or if it was because of the type of wood used, but it was massive. The water turned thick. When I did the water changes, the glass remained covered in goo and created a very weird optical effect. More importantly, the foams used in the HMF clogged and the filter kept collapsing. I had to wash it a few times as well, which I was hoping to avoid, since it is supposed to be maturating. Alas, this as well is improving and after the last water change it looks like it is again manageable. The filter stopped collapsing.

During all this time, I managed to get 2 ammonia readings only, because the painted water was getting in the way of seeing the right colors. Both tests gave zero ammonia, which I think is weird, but whatever... pH is somewhere between 6.8~7.0, so all this brown drama did nothing to acidify the water. TDS is now remaining between 90 and 100ppm. KH between 0.5 and 1.0dKH, the same as the tap water.

On sadder news, I bought 7 Corydoras nijsseni but they near immediately died in the quarantine. Only one survived. The quarantine itself should be more than adequate, I have some Bloody Mary shrimps in there and they are fine. It is a very mature slightly planted tank. The Corys formed large red blotches on their sides and I'm thinking that I may have handled them poorly when removing from the plastic bag, they panicked and may have stabbed each other when I was trying to pick them up. Now I'm embarrassed to go back to the LFS and buy more. I'll wait for the tank to be ready and to be sure that the last one survives.

 

[OllieTY]

Without knowing what that wood is made of, you could be dealing with this intense tannin staining for months...

 

[LMuhlen]

A quick update, my surviving cory is looking smart, so it is very likely that it will make it to the tank eventually. It shows to me that the quarantine is adequate and there must have been some wrongdoing during transport or acclimation.

The water in the tank is no longer a stain risk for my clothes. Some brown spots formed on the glass and on every surface, at first I thought it was algae, but it is not attached. It looks like brown water condensed and coalesced... maybe some microbial colony that fed on the black water substances? In any case, I'm not worried about that, but the water is still milky and I hoped that it would be clear by now. I won't start adding any fishes until it clears. I think it may be related to whatever sugars and other juicy stuff that leak from the woods and feed the typical white goo on new wood. The white goo itself is now under control, behaving as expected, only growing very slowly. I'm hoping that a few more drastic water changes will fix this too.

I've had the opportunity to validate the safety of my selection of dried leaves. When I assembled this tank, I filled a smaller one that was left unused, mostly to prevent any issues with the silicone drying, and set it as a future aid for WCs. I added some of each of the leaves used to make the water ready for water changes, but since I only did full water changes so far, I haven't used this water. And then some fish in my main tank had fry and, not knowing what to do, I moved a few of them to this support tank. It has been more than a week and they all look well. If the fry survived the leaves, they must be safe. The fry left in the main tank are all gone, most likely.

 

[Fiske]

That's-- a lot of tannin. Whoah. I envies a bit.
Not to rain in your beer, but since I've recently been down a wood rabbit hole; the branches you have used look an awful lot like grape vines. If that's the case, be aware that they might not last long. I have no experience with them in aquaria, but the vivarium/terrarium folks (at Dendroboard.com) say they are prone to rotting. I have some in one of my vivariums, and so far it's holding up, though.

 

[LMuhlen]

the branches you have used look an awful lot like grape vines. If that's the case, be aware that they might not last long.

Yes, that is a risk I'm aware of... I don't know what kind of vines they are, they all look the same to me, but this tank is also meant as a test for what could be a larger discus tank in the future. If the vines do well, it will be a great addition for this future tank, and if they rot, it's a lesson learned. There is a guy in my town who has a tank with vines just like these, and he's had them for a very long time, and I think that I bought mine from the same supplier, although after a few years there is no telling if the vines he sells are of the same kind.