Nano fish are an exciting, underappreciated segment of the aquarium hobby. These are fish that stay under 2 inches in size, making them perfect for aquariums 5-10 gallons in size. A few are hobby staples, such as the Neon Tetra and Guppy.
However there are many that are very uncommon despite having been around for a very long time. The Scarlet Badis is one such hidden gem. Considering its brilliant color and shy personality the phrase is especially well suited to this tiny percoid fish.
What is the Scarlet Badis?
Scarlet Badis are among the smallest of the percoid fish, a superfamily that includes such familiar faces as the Yellow Perch (a North American gamefish) and the marine Basslets.
Depending on how old your sources are you may also see the Scarlet Badis described as Badis bengalensis, an older name that’s since been replaced by Dario dario. Previously it was grouped in the genus along with Badis badis, the similar looking but larger Blue Badis. Dario is reserved for the Scarlet Badis plus a few close kin in China, India, and Southeast Asia.
Badids like the Scarlet Badis are fascinating little fish that are similar to Dwarf Cichlids in habit. They are shyer but just as territorial towards each other, especially the males. They also care for their eggs in much the same way as cichlids.
If you can get your hands on a small group the Scarlet Badis is an excellent nano fish to start with.
- Common Names: Scarlet Badis, Gem Badis, Rainbow Badis, Bengal Badis
- Scientific Name: Dario dario
- Origin: India
- Length: ¾ inch
- Aquarium Size: 5-10 gallons
- Ease of Care: Easy
- Temperament: Peaceful; Territorial
Caring for Scarlet Badis
This section covers various Scarlet Badis care topics such as aquarium size, water parameters, diet, and more.
Being so tiny you can easily house 1-3 Scarlet Badis in even a 5 gallon aquarium. However a lot of this depends on the sex ratios you end up with.
Males are brilliantly colored and much larger than females making it easy to tell them apart. But they are viciously territorial and a subdominant male that can’t escape from a losing fight will be harassed to death in such a small tank.
If keeping them in anything under 20 gallons you’re limited to a single male plus 2-3 females for him to show off to. In larger aquariums you can generally house one male per 10 gallon so long as you have plenty of breaks in line of sight like plants and driftwood.
They will spar with each other frequently regardless of how large your aquarium is. But so long as the loser can break off the fight and retreat the spats will be interesting but harmless.
An alternative approach that many Badis keepers favor is to keep a large colony of Scarlet Badis. Much like African Cichlid tanks, this ensures the aggression is spread out. This prevents any one fish from becoming too dominant or any one male from becoming too abused.
In this case, we want 6-10 Scarlet Badis, with at least 4 of them being males. Your tank should be at least 20 gallons in size to ensure they still have space to form their territories.
Personally, I prefer giving the males plenty of space. But considering how small their bioload is and how beautiful they are, you may decide you want a good-sized group!
Scarlet Badis need moderate water conditions in terms of chemistry and temperatures. As tropical fish, 74-80℉ best suits them, with a few degrees in either direction still being comfortable.
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Remember that nano tanks can swing in temperature much faster than larger aquariums due to the smaller volume of water. So don’t rely on room temperatures if you live in a region known for cold snaps. Fortunately, even the least expensive modern nano tank heaters provide plenty of capacity (5 watts per gallon)
Chemistry-wise, they prefer a pH of 6.5-7.5; slightly acidic to slightly alkaline. The closer to neutral (pH 7.0) you can balance the water chemistry, the better!
If you live in a region with hard, alkaline tap water, using a substrate rich in plant matter, driftwood, or adding Indian Almond leaves can all help buffer the chemistry down towards acidity.
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Ammonia, nitrite, and nitrates should be as close to 0ppm as possible. While not especially sensitive you still don’t want continuous exposure to these agents. Elevated nitrogenous wastes cause stress and can open fish up to disease even if it doesn’t outright kill them.
Plants & Substrate
Scarlet Badis really should be kept in aquariums with live plants. In sparsely decorated environments they become extremely shy and willing to retreat from their hiding places. However when they know they have a safe retreat nearby they become much bolder and more willing to stay out in the open.
Given their preference for mild water conditions they can live alongside nearly any aquarium plants in the hobby. Best of all, they are entirely plant-safe and have none of the digging habits of Dwarf Cichlids.
Some of the best plants to keep with Scarlet Badis are carpeting plants like Dwarf Baby Tears (Hemianthus callitrichoides) or Monte Carolo (Micranthemum sp.). If you prefer low light plants that don’t require specialized lights, carbon dioxide fertilizer, or other supplements, try easy plants like Java Moss (Vesicularia dubyana) or Anubias (Anubias sp.).
These plants are epiphytes, meaning they can be attached to rocks, driftwood, and other hard surfaces. This means you don’t need to spend extra on enriched planted aquarium substrates.
Speaking of substrates, Scarlet Badis are also unpicky when it comes to sand versus gravel. Any substrate will work just fine for them. It’s best to make your decision based both on aesthetics versus which will work best for the plants you have in mind.
Rocks and driftwood are also good to have in a Badis tank. Rocks provide an excellent contrast to the plants and fish with their mineral textures and angled edges. And driftwood is a place for both biofilms and epiphytes to grow as well as a valuable source of plant tannins.
Tank Mates for Scarlet Badis
Choosing tank mates for Scarlet Badis takes a little time to work out but thankfully isn’t too big of an issue. The main considerations should be choosing fish that are just as small and are entirely peaceful. Fortunately, nearly any fish that’s around the same size is a great fit for Scarlet Badis.
There are many schooling and shoaling nano fish to consider. A few of my favorites include the Chili Rasbora (Boraras brigittae) and the Celestial Pearl Danio (Danio margaritatus). These fish are both brilliantly colored and enjoy the same invertebrate-based food as Scarlet Badis.
Sparkling Gouramis (Trichopsis pumila) and Chocolate Gouramis (Sphaerichthys osphromenoides) are also at home in the environments favored by Badis.
Pea Puffer fish are unique, fascinating to watch, and easier to find in the hobby nowadays. They can be a bit moody and are voracious predators of small shrimp and snails. However they are generally well behaved nano fish with loads of personality.
Lastly, other Scarlet Badis make great tank mates, assuming you’re careful to plan for it. You’ll get much better color out of your males and spawning activity from your females in a properly sized and aquascaped tank.
Most smaller bottom dwelling fish will do great alongside them. Corydoras are active, peaceful, and schooling. A few may grow intimidatingly large so stick to the smaller types such as the highly social Pygmy Corydoras (Corydoras pygmaeus).
Poor tank mates for Scarlet Badis include large (2+ inches), territorial, or predatory fish. Considering Scarlet Badis rarely get larger than ¾ inch, what’s considered “predatory” may surprise you.
Remember that most fish are opportunists. Even mostly peaceful fish like Angelfish will gladly snap up a tasty nano fish. Large predators like Catfish and medium sized to large Cichlids should obviously be avoided.
Dwarf Cichlids are similar to Scarlet badis in a lot of ways but are best avoided. Most Dwarf Cichlids grow quite a bit larger (2-3 inches) and are aggressive towards fish that look similar, such as the Scarlet Badis.
Unlike Pea Puffers, Scarlet Badis are mostly invertebrate safe. They may occasionally eat newly hatched Red Cherry Shrimp. But after a few weeks the young will be too large to be eaten. And a happy colony of shrimp will have more babies than your Badis will ever eat. They also don’t bother snails or clams.
Great Tank Mates for Scarlet Badis
- Guppies, Galaxy Rasboras, Chili Rasboras, Sparkling/Chocolate Gouramis, and other Nano Fish
- Smaller Tetras
- Pea Puffer fish
- Kuhli Loaches
- Corydoras, Otocincus, and other small bottom dwellers
- Dwarf Shrimp & Snails
- Other Scarlet Badis
Poor Tank Mates for Scarlet Badis
- Angelfish, Gouramis, Barbs, and other medium sized community fish
- Predatory and Territorial Fish
- Multiple male Scarlet Badis in aquariums under 20 gallons.
Feeding Scarlet Badis
Scarlet Badis are known as micro predators. This means they prefer feeding on tiny free swimming invertebrates that are found in huge numbers in natural waterways.
The menu can include tiny micro worms, water fleas (daphnia), newborn shrimp, mosquito larvae, bloodworms, tubifex, etc. They also enjoy eating young fish fry and any eggs they stumble upon.
The key here is the word “micro,” however. They are carnivores but you need to provide appropriately sized prey items. Fortunately, most of the food listed above is readily available in aquarium stores.
Most live food can be easily grown at home or kept fresh for extended periods. I highly recommend keeping some on hand, especially if you intend on breeding your Scarlet Badis. Live food also helps encourage picky, newly introduced Scarlet Badis to feed.
You can also supplement their fresh and frozen diet with prepared foods. Even the smallest fish pellets may be too large for them so make sure that it’s formulated for nano fish. Crushed flake may also work but fresh and frozen food gets their attention like nothing else.
Breeding Scarlet Badis
Breeding Scarlet Badis is not especially difficult once you have a stable group that’s happy and well-fed. As I mentioned earlier, they prefer very moderate water conditions so try and get things as close to neutral as possible.
Adding sources of plant tannins can help buffer hard tap water towards acidity, which is important because you’ll want to perform fairly frequent large water changes. These simulate seasonal shifts in water level and chemistry, signalling that it’s time to begin preparing gametes (eggs and sperm).
Sexing Scarlet Badis is extremely easy until it isn’t. Males are a brilliant crimson in color while females are a drab grey to brown, sometimes with faint red bands. However subdominant males often do their best to imitate females to avoid being chased by a dominant male.
That said, they can only change their appearance so much. Males are still roughly 30% larger than females when fully grown. They also have an iridescent blue stripe that runs the length of their pelvic fins, which also have slight extensions. Both of these features remain even in subdominant males.
Sexing juvenile Scarlet Badis, which are typically what you get in pet stores, is unfortunately next to impossible. Your best bet of breeding them is to buy a small group and watch as they mature.
Once it’s clear which are the males and females, you can separate them out if you only want one male. Or simply let them form their territories and eventually they will spawn.
Scarlet Badis provide basic parental care for their eggs, a trait that’s fairly rare in fish besides Cichlids. Once the male and female spawn, which is usually done over a small pit dug into the substrate, the male will watch over the eggs until they hatch, which takes 5-7 days.
After this point the fry are left to their own devices and should be removed as any passing fish will quickly eat them. The fry will spend the next 2-3 days absorbing their yolk sac after which they become free-swimming.
Once you see them moving about, introduce to them cultured infusoria as a first food. They are simply too tiny to take anything else. Within 1-2 weeks they will have grown in size and they can eat live baby brine shrimp nauplii and micro worms.
From there, you need only to keep feeding them until they grow large enough to be reintroduced to the main aquarium!