Blackwater aquariums are becoming more popular but probably something you have only seen rather than tried yourself. A blackwater aquarium is a recreation of one of the most natural habitats for fish. You are very unlikely to find many rivers or waterways that have clear water. Instead the water you are likely to find is a murky bottomed river with a covering of decaying leaves and wood. The term black water is used for the dark color of the water. This darkness is present due to the release of tannins from the decaying driftwood and leaves at the bottom. The more tannins that are present, the darker the water. What is also unique about blackwater aquariums is that the pH tends to be lower than a clear water aquarium and the water is also very soft, both these aspects are as a result of the tannin in the water which naturally make the water acidic and soft.
Some quite spectacular visuals can be created from a blackwater tank with cleverly placed lighting spilling through the darkened water and plants. An environment that your fish will find very comfortable, natural and relaxing.
How to setup a blackwater aquarium?
So we know that we need to create tannins to discolor the water. One thing to be mindful of is your usual nitrogen cycle, as it is important that nitrate levels still remain controlled. I would recommend your usual process for the nitrogen cycle initially.
Next, substrate. As you are trying to recreate that natural river bottom I would simply use sand, if anything, at the bottom of your tank. Then introduce decaying leaves and driftwood. Driftwood is an absolute essential part to any blackwater tank. What you will find is that over time, as the tannins are excreted from the decaying plant matter that the water will turn progressively more brown in colour. Please do not expect blackwater, though the darkest brown can appear black but this is very difficult to achieve as the pH will be very low and the water very soft. Only carefully chosen fish will thrive in this environment.
Carefully monitor pH and hardness levels. What you are aiming to achieve is pH below 7 down to around 5. Getting below this to properly replicate the natural pH of rivers of around 4.5 is very difficult. You will need to achieve hardness around 5 to 10 degrees.
Please remember that it can take a little more time to set up a blackwater aquarium opposed to a clearwater aquarium so be patient with the process as the results can be quite spectacular.
How to light a blackwater aquarium
Lighting can be used in very clever ways within a blackwater aquarium to enhance the moody river bottom affect with the floor of the aquarium being a mix of dark shadows and small bursts of light. This can really make the aqaurium look and feel that you are recreating the visual of natural sunlight through the water.
The golden rule is to use low light which will help create your moody shadows. A 6500k to 10000k bulb with 1 to 1.5W per gallon can provide this perfectly.
Lighting placement also plays a part in creating the right mood for your aquarium so play around until you are happy with the affect you are trying to achieve.
What are the best fish for a blackwater aquarium?
A blackwater aquarium can sigificantly benefit fish that have come directly from the wild as you will be introducing them to an environment that already feels familiar and comfortable. It is very important that you understand the acidity and softness of your water so you can carefully research the correct fish to have in your tank.
When choosing your fish, as well as considering those that prefer a more acidic setting, also consider which fish can live together. For example, Bettas thrive in this environment but you are likely to restrict what other species you can then place with your Bettas.
Catfish absolutely love the blackwater environment however do remember that catfish will eat anything that fits in its mouth - including other fish!
Neon tetras again will thrive in blackwater. These also provide exteremly pleasant viewing. Do remember that tetras are schooling fish so be sure to introduce a handful at a time.
Dwarf Cichlids are also a good choice. This fish are particularly easy to breed so that could be a consideration for you.
Gouramis work well in blackwater as this is their natural environment in the wild. Chocolate gouramis in particular seem to be popular.
Angel fish is another breed that, in the wild, originates from a blackwater environment. Again, this fish is fairly easy to breed so alongisde the fun of having a blackwater tank you can also try your hand as a breeder!
Pencil fish is also another fish to consider. Their glittering scales can provide flashes of light as they pass through any bursts of light you allow in your tank. Please make sure you do not mix Pencil fish and tetras! Two schools of fish in the same tank does not always work and pencil fish can be quite sensitive to their environment so can take extra time and effort to keep happy.
What are the best plants for a blackwater aquarium?
Plants, along with lighting really do play a vital part with the visual aspect of your blackwater aquarium. Remembering that you are trying to replicate a sandy river bottom this is a good place to start when chosing your plants. Whether you choose live or artificial plants the affects can both be tramatic.
So you have your driftwood and old leaves placed in the bottom of your tank. The next consideration is to have mildly dense, but tall vegetation. Java Fern and Amazon Fern are just perfect for this setting. Scatter some Anubias around so the taller plants do not completely dominate, these look fantastic with driftwood as their base.
Water lettuce can provide a carpet of green in your aqaurium that can help bounce the light around in a different way too.
How do I do a water change for my blackwater aquarium?
As with all aquariums consistent water changes are good regular maintenance practice and blackwater aquariums are no different.
Specifically for blackwater aquariums a recommended water change of 20% weekly. The trick with blackwater aquariums though is to let old leaves soak in water ahead of the water change. A pre-soak if you like! This will spring start the decaying process and release the tannins in to the water before you put it in your tank. What this helps avoid is a spike in your pH from any rapid release of tannins in to your tank.
I would still recommend adding a couple of old leaves directly to your tank, but be sure to keep an eye on your pH and nitrate levels.
How do I maintain my blackwater aquarium?
Blackwater aquariums can often be misunderstood as 'dirty' water tanks. This could not be further from the truth. There are three main areas that arguably need more attention than a clear water aquarium. Firstly, keep a close eye on your nitrate levels. Maintaining good bacteria is a must in any tank but because blackwater tanks are subject to what can be rapid changes you may need to spend more time ensuring your nitrogen cycle is maintained. Next, your pH levels. I have mentioned this a lot in this article. The higher your tannin levels the more subject to rapid change your tank is subjected to. Lastly, water softness. Tannins greatly affect water softness and so you must stay very tuned in to this reading on a continued basis.
Overall keeping a blackwater aqaurium can be extremely rewarding. For you, the visuals can be wonderful but more so for the fish you are keeping and putting them in to a natural environment can see them thrive.