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Just converted to a blackwater set up. New sand, rocks, driftwood. I want a more authentic tank with an Asian blackwater style look for my silurichthys indragiriensis. I have two cichlids, two koi angels and 1 female sword tail and they are loving this set up.
Maybe someone could tip me as to what to include ? I'd like to remove the fake plants, too.
Thoughts?

For a more authentic look, you should remove all the plants (fake or real) entirely. There are no submerged aquatic plants in Asian blackwater habitats, save for bladderworts (Utricularia).

I'd suggest removing all the other fish (save for the catfish) if you want to recreate the biotope, but I gather that's not your aim.

Ultimately, yes, I would like to remove all f them. One angel is a complete bully, the cichlids have no personality and I love the little female sword but she's got no friends.
What type of fish might I stock with? What would accompany the catfish w/out out growing my 20g?

that is a lot of fish if that tank pictured is 20 gals. i thought it was bigger. i agree with above posters, although the plants in there do look very nice right now.

leaves are a great way to help water conditions match. i would use different color/shape rocks though if you can find any good ones. otherwise keep the current ones in there until you find cooler ones. they need to look more natural.

replace the plastic plant with even more driftwood to cover up the left back side equipment. the more driftwood in the background, the better.

if you want smaller fish, try flame dwarf gouramies and harlequin rasboras.
otherwise a pearl gourami would look good as centerpiece. with some sort of schooling fish like harlequins. a lot of barbs are also from Asia i think.

Rather than how it looks, the most important thing about a blackwater tank is amount of minerals in the water. There should be a zero or very low concentration, meaning RO or deionised water must be used.

This will be very unsuitable for the swordtail, and probably the cichlids too, depending on the species.

RO isn't that necessary. but if you want to be a diehard perfectionist and keep sensitive blackwater fish then yes it would be good to limit KH and GH to recreate as natural an environment for them as possible. most fish are hardy enough to live and maybe breed in harder tap waters.

I sort of consider my 40 gallon a SA blackwater tank but it's more just SA fish than it is pure blackwater biotope. (minus my platy.)

Hi all,

RO isn't that necessary. but if you want to be a diehard perfectionist and keep sensitive blackwater fish then yes it would be good to limit KH and GH to recreate as natural an environment for them as possible. most fish are hardy enough to live and maybe breed in harder tap waters.

It isn't really about being a perfectionist, I don't think you will breed many black-water fish in harder water, or that they will live long lives. I keep all my soft water fish in planted tanks, even though they often aren't biotope specific, because they makes maintaining water quality easier, but

is amount of minerals in the water. There should be a zero or very low concentration, meaning RO or deionised water must be used. This will be very unsuitable for the swordtail, and probably the cichlids too, depending on the species.

"Racoll" is trying to do his best for you and your catfish here.

Have a look at Colin Dunlop's article, it is a good read: <http://www.seriouslyfish.com/all-the-leaves-are-brown/>.

cheers Darrel

Yea I love using dried leaves in my tank. I normally use Indian Almond leaves since i have a bunch of them from when I used to breed bettas (Yes bettas do breed in hard alkaline water with the help of leaves to lower the pH slightly and remind them of their natural water conditions they have evolved to).

My BN plecos love eating them too, i have raised a lot of fry that decimated my leaves. i think it's very good for them to eat it. good for shrimp too.

The only issue i have with RO/DI water use is that it gets tedious and expensive mixing it each week. if you mess up, you end up with either too much GH and KH or too little. also if its a heavily planted tank, and you are not diligent with water changes you might run into trouble after a long overdue water change if using tap water (its recommended to use mostly RO water for the water change because of nitrogen differences in tap water VS heavily planted tank water devoid of nitrogen. nitrogen concentration differences will kill fish. often see with people losing fish randomly after large water changes. "But all parameter levels were perfect!" is what you normally hear).

I'm just lazy lol. and i don't have money to keep true low GH/KH tanks. to those that are dedicated enough, kudos to you. you should be able to keep more difficult fish w/o problems. I'll stick with my angelfish and simple tetras and tolerant plecos (BNs and L260).

.Plecomania. wrote:most fish are hardy enough to live and maybe breed in harder tap waters.

Most yes, with the exception of wild-caught strict-blackwater fishes. They typically do badly in water with any appreciable level of minerals.

.Plecomania. wrote:The only issue i have with RO/DI water use is that it gets tedious and expensive mixing it each week

I don't bother with adding back in any KH or GH, and just use RO neat. Never had a problem or a "pH crash".

but aquariums do need SOME KH and GH in order to survive. where are your minerals coming from? they have to come from somewhere. maybe food? stuff like calcium and magnesium? even if KH is say 0 or close to 0 in a good blackwater tank, there should still be around 1-2 or 3 dGH in there for red-ox processes in the tank.
agree some soft water fish i just cannot keep. i wouldn't even attempt discus, and even my cardinal tetras which were wild caught did not do very well. i only have one left.

It's easy enough to maintain a small amount of GH/KH by maintanining by decorating the tank with certain rocks or gravels, like aragonite, or a bit or rock containing magnesite. A pinch of epsom salts would do the trick too and is dirt cheap. That's what we do out here on the Canadian west coast where the GH and KH is less than or equal to 1.

but aquariums do need SOME KH and GH in order to survive.

Not in my experience, and my blackwater fishes (and plants) thrived.

I'm sure Darrel can explain this better than me.

then you must be dosing for the plants. which provides the GH for the fish.

Hi all,

but aquariums do need SOME KH and GH in order to survive. where are your minerals coming from? they have to come from somewhere. maybe food? stuff like calcium and magnesium? even if KH is say 0 or close to 0 in a good blackwater tank, there should still be around 1-2 or 3 dGH in there for red-ox processes in the tank.

Black waters are different
"Racoll" is right black waters are different, and so are the fish that live in them. Some level of dKH/dGH makes tank management easier, but they aren't required by the fish. Dissolved Organic Carbon (DOC) and leaf litter can build up in black water because of the low pH, and the very high Carbon:Nitrogen ratio, which means that decomposition is very slow, even at higher temperatures.

Black water chemistry
If you look at the water chemistry figures these are waters with virtually no salts of any description. I haven't got figures for SE Asia, but these are for Amazonian Rio Negro <http://www.scielo.br/scielo.php?script= ... 0000300015> and as you can see conductivity levels (all ions) are often less than 20 microS.

Aquatic productivity
Black waters have fairly low productivity, because of the lack nutrients, and may have very little aquatic vegetation (because of the tannin staining, low pH and low nutrient levels) and those plants that do occur (Utricularia, Tonina, Brasenia, Eriocaulon etc.) are adapted to these conditions.

Biological filtration
Biological filtration is also compromised, mainly by the non-availability of carbonates (HCO3-). This isn't a problem in natural systems, mainly because the humic compounds reduce bacterial growth and there is little bioload. In the tank, where we have much higher stocking than we would in nature (even if we are very lightly stocked) this can be a problem and it makes water management more difficult. Plants and dKH/GH make life a bit easier, but you don't actually need them, and you can use 100% RO as long as it has some humic compounds.

Plants
I have plants, they help maintain water quality in small water volumes, partially by stopping ammonia entering the compromised biological filtration system. If you don't have plants you need to be very good at water management.

pH, why it isn't really relevant

Never had a problem or a "pH crash"

If we have water very low in TDS, then pH becomes a fairly meaningless measurement.

In the case of water with a lot of tannins, the DOC level will be closely correlated with pH, and as DOC levels rise pH will fall, again we haven't actually added a lot acid (H+ ion donor), but we don't have any carbonate buffering (H+ ion acceptor) to counteract this. If we have a system with very soft water and submerged plants we get huge variations in pH as the CO2 (as H2CO3) and oxygen levels (O2, but oxygen is the base in O-H), this isn't a problem for soft water fish. When people have pH crashes it is is because acidosis has lowered the pH and killed the fish, low pH and fish death are both symptoms of the underlying problem, not cause and effect.

pH is a ratio
pH is just the ratio of H+ ion donors: H+ ion acceptors, it doesn't tell us anything about amounts or buffering. In buffered salt rich systems (like Lake Tanganyika or sea water (53,000 microS)) small changes in pH reflect large changes in chemistry, conversely in very soft water large changes in pH reflect small changes in water chemistry.

It is water chemistry that effects the fish, not pH directly.

cheers Darrel

Very informative, thanks

Great post Darrel. This should perhaps be some sort of FAQ article. It dispels many myths about soft water systems and blackwater biotopes.

It is not true that nitrification by bacteria does not take place in very acid waters. While such waters do inhibit many bacteria, the ones responsible for nitrification are not ones that becomes absent in such water. I would point folks to the following research on this topic.

Changes in ammonia oxidiser population during transition to low pH in a biofilm reactor starting with Nitrosomonas europaea
http://gwri-ic.technion.ac.il/pdf/Profe ... een/11.pdf

High-Rate Nitrification at Low pH in Suspended- and Attached-Biomass Reactors
http://aem.asm.org/content/70/11/6481.full

Nitrification in a Biofilm at Low pH Values: Role of In Situ Microenvironments and Acid Tolerance
http://aem.asm.org/content/72/6/4283.full.pdf+html

I keep altum angels and do so in black water tanks. While they have been moved up to a pH of 6.0, thy were started at 4.2 when they arrived and moved up to the 6 level over about 4 months. I use ro/di water mixed with my tap and run the tds in the 70 ppm range. I use rooibos tea, catappa leaves, alder cones, peat and muriatic acid to maintain the parameters and staining.

Hi all, "TwoTankAmin" wrote

It is not true that nitrification by bacteria does not take place in very acid waters. While such waters do inhibit many bacteria, the ones responsible for nitrification are not ones that becomes absent in such water. I would point folks to the following research on this topic.

Thanks for the links, they are very useful.

showed that the nitrifying bacteria were from the monophyletic genus Nitrosomonas, suggesting that autotrophic nitrification at low pH is more widespread than previously thought. The results presented in this paper clearly show that autotrophic nitrifying bacteria have the ability to nitrify at a high rate at low pH and in the presence of only a negligible free ammonia concentration, suggesting the presence of an efficient ammonium uptake system and the means to cope with low pH.

Sounds pretty unequivocal (From the linked Tarre & Green paper).

So I think the other half of the answer is that populations of specialized nitrifying bacteria (like Nitrosomonas oligotropha) will build up over time (60 days is mentioned) in the filter and upper layers of the substrate, and that biological filtration isn't necessarily compromised (at low pH) once these microbial communities have formed.

cheers Darrel