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The Roseline Shark, or Denison Barb, is a medium-sized schooling fish with a lot of personality. While they’re relatively easy to keep there are some caveats to their care and their presence in a tank should always be well-planned. Done properly, even a beginner should easily maintain a thriving population in no time.
So, let’s dive right in with some information to help you out with Roseline Shark care!
Roseline Shark Quick Care Sheet
- Common Name: Roseline Shark
- Alternate Common Name(s): Denison Barb, Torpedo Barb
- Latin Name: Sahyadria denisonii
- Care Level: Moderate
- Tank Size: 55 Gallons+
- Size: 5”
- Diet: Omnivorous
- Behavior: Peaceful
- Lifespan: 5 Years
- Reproduction Type: Egg Scatterers (See Below)
- Water Temperature: 72-82°F (22-28°C)
- pH: 6.5-7.5
- Water Hardness: 5-25 dGH
Origins of the Roseline Shark
The Roseline Shark, or Denison Barb, is a medium sized shoaling fish that finds itself in aquariums frequently despite being a new addition to the trade. They’re native to fast-moving rivers and streams in the Western Ghats of India.
These fish are endangered in the wild, mainly due to their collection for the pet trade. They’re also notoriously hard to breed in captivity. That’s not to say you can’t find them ethically, but they’re not as easy to find as something like Cherry Barbs (also endangered in the wild) since breeding them at home is incredibly hard. Commercial operations have had some success through extreme measures.
The Roseline Shark is a cyprinid, which means that it’s a barb. It’s among the calmer of the species, but it still displays some gregarious behavior. These are not shy fish, indeed they can even cause problems for slower fish just by virtue of their high activity levels.
There is one confirmed variation of the species; the Golden Denison Barb. It has a gold tint to the color and the coloration appears to have been natural rather than the product of human meddling. Sadly, the golden variant is now extinct in the wild although specimens can still be found by those willing to dig a little bit.
These fish require two main things: a school to swim with and a lot of room to do the swimming. Much like the various Danio species, the Denison Barb likes to dart and needs a long run for its own health. A 48” 55-gallon long tank is a great start, but you may want to consider something even bigger.
Due to their tight shoaling, the Roseline Shark should never be kept alone or in small groups. Six is the minimum number of these fish, but twelve or more is better. Sharks kept in smaller groups will suffer from stress and it will shorten their lifespan. Stressed fish display worse colors and are less active than their healthy counterparts, so keep that in mind before choosing a tank.
In the wild Roseline Sharks school in hundreds or thousands. You can’t pull that off in your fish room, but you can do your best to accommodate their social needs with a larger tank to hold the shoal.
The single biggest mistake made with the care of these fish is putting them in too small of a tank. Their swimming habits mean they need more room than most similarly sized fish, so it’s a good idea to go a bit bigger than you think is necessary.
Due to their natural habitat in fast-moving streams, there are a few minor caveats to their care. A high flow rate is desirable, but it also keeps us from keeping some other fish, and the water needs to be highly oxygenated. I normally switch out air pumps for live plants, but it’s still a good idea to use an air pump in this case.
Their natural environment does have plants and some hiding places, but these are only important considerations for other animals in the tank. Roseline Sharks are live-plant compatible but you need to take some extra steps I’ll detail below.
The key points you need to remember when dealing with these fish are simple:
- Always ask your source where the fish came from. Commercial breeding operations supply most, but you don’t want to contribute to their population decline in the wild.
- Roseline Sharks require a lot more space than their size indicates. 48” is the minimum length for a full-grown specimen.
- Extra flow and a good air pump are good ways to help keep the fish healthy.
- Plants and hardscapes are a good idea but not required. Some special steps should be taken to protect the plants.
- Roseline Sharks are almost impossible to breed in the home aquarium.
- These fish shoal in hundreds to thousands in the wild, making them unsuitable for being kept in small numbers.
- These are peaceful fish, but very active, which is a consideration when you’re choosing tank mates.
So, now that we know where they come from and the challenges we face with their care, let’s talk about surmounting those challenges.
Ideal Tank Setup
There are very few cases where the Denison Barb isn’t the top priority in a tank due to their size and requirements. An ideal tank will still support a wide range of tankmates, but it’s not an ideal environment for every type of fish either.
You’ll need the usuals to set up the tank.
- Aquarium- Long is better in this case. A 55-gallon long (ie: 48” long) is the minimum you should keep these fish in, but going up to 72” or more is better if you have the money and space for a larger tank.
- Filtration System- Aim to double the rated capacity of your filters to increase the flow rate of the tank. Canisters are ideal for creating a one-way current, just make sure to put a filter sock over the oversized intake to protect smaller creatures.
- Heater- The proper size for your tank. Use our wattage calculator if you’re unsure of the correct size.
- Air Pump- You can use one that’s correct for your tank’s size. Fine diffusers should be used to maximize gas exchange with the bubbles of air and increase the water’s oxygenation.
- Powerheads(Optional)- Used to create even more flow in the tank if desired. They’re a great idea but with a powerful enough filter you can bypass them.
You’ll also want to pick up your substrate, hardscape, and any live plants at the same time. We want to get the plants in early for the reasons detailed below.
Make sure your tank has a secure hood as well. While not known for jumping, it does happen and a full-speed Denison Barb can move a long way after breaking the water’s surface.
Consider Activated Carbon Carefully
Activated carbon is an awesome filtration material, but you should be careful about using it with a school of Roseline Sharks. It won’t harm them, but you should be able to remove it easily and replace it with another stage of filtration. It’s going to be a pain if it’s buried deep in your canister.
The reason for this is simple: these fish can get sick easily if nitrates are high and diseases will quickly spread to all of them. Activated carbon will strip medications from the water, and you don’t want to put off digging it out of the bottom of your filter when time is of the essence.
If you keep it as the top stage in most filters it can be removed in seconds, allowing you to dose medications without worrying about them being sucked into the carbon.
The Roseline Shark isn’t going to eat your plants, for the most part, but you need to be careful or you’re going to end up with a lot of plants floating each evening.
My biggest piece of advice is to plant any stem or rhizome plants before you add the fish. A week or two before at least. Preferably when the tank is cycling if you’re planning on using a new aquarium to house them.
The Denison Barb is large and moves very quickly. They can also be a bit “playful” with plants. This means stem plants that aren’t well-rooted can be torn from the ground and scattered around the tank over the course of the day.
A good couple of weeks of rooting will help your plants to stay put when the fish are swimming, or if they decide to tear at them.
Plants like Anubias sp. or Java Fern should be tied off to the hardscape. Clear fishing line works well and will continue to hold the plant indefinitely. You can also use cotton string, which will rot away eventually, but the plant should be well-rooted on the rock or driftwood by then.
Ground covers work well, the shorter the better. You can also cover the bottom of the tank in something like Cryptocoryne wenditii which has extensive root networks and remains short.
If you choose to add stem plants after the fish you should probably weigh them down. If you keep the weight above the substrate level it can be removed in a couple of weeks when the plant is rooted enough to stay in place.
Try to avoid extra tall plants. They don’t fare well in the high flow rate environment and they can interfere with the Sharks’ swimming room.
Caves are always a good idea, and they’re a basic requirement for community tanks. Careful use of rock and driftwood can also help the entire aquascape come alive, creating a dynamic environment for both plants and animals.
It’s not something that we should neglect here, but we may need to take a different approach.
The key here is to keep the upper 50-75% of the tank clear of obstructions. We also don’t want floating plants on the surface. Plants should also be trimmed back, but a few tall Vals or a single Echinodorus sp. is fine.
You can do this while still providing plenty of cave space for loaches, catfish, and other bottom-dwellers. Use plastic barriers to “hollow out” areas underneath logs and rocks, creating caves inside the substrate for these fish to use. The plastic barriers, generally just cut strips of 1mm plastic, also prevent the caves from collapsing if the substrate moves a bit.
Water Change Schedule
Make sure that you change the water regularly with these fish, rather than just topping it off. That includes those tanks with a lot of plant life, that otherwise might be fine turning a weekly water change into a monthly one.
The reason for this is simple: the waters of the Western Ghats that the Roseline Shark calls home are very clean due to being near the source and fast moving. If you look around, you’ll note that some people seem to believe that Roseline Sharks are very prone to disease.
That’s not quite the case. Many times it’s simply due to water not being clean enough for them.
Stick with a 25-30% weekly water change for the best results. While these fish can do well in many conditions, the one thing they won’t tolerate is dirty water.
Cycling the Tank
Never cycle a tank with Roseline Sharks inside. They won’t survive a full cycle without extreme measures (ie: multiple daily water changes).
If you’re new to the fishkeeping world then you should read up a bit on the nitrogen cycle. Cycling the tank is the same as any other, except we’re going to try to reduce nitrates farther than normal before introducing the fish.
Cycling should be done as follows:
- Setup the tank normally, including placing plants.
- Add a small amount of fish food daily.
- Begin testing for ammonia. When ammonia shows up, continue testing daily until it no longer shows on your test.
- Begin testing for nitrites daily, continuing until the levels are unreadable to your testing kit.
- Begin testing for nitrates daily. For these fish we’ll be aiming for <15ppm at least and preferably as low as possible. <10ppm is preferred, anything over 20ppm needs to be addressed before adding the fish.
- Add the fish in slowly over a few weeks. If you can, add 3 initially and then 1-2 per week until you have the school size you’re aiming for.
I normally don’t worry too much about nitrates in tanks, especially those with plants, but in this case, we want very clean water. If nitrates remain high you have a few options:
- Check your tap water source before adding it to the tank. Some municipal water supplies have a considerable amount of nitrates without filtration.
- Ensure that your filters are enough for the tank. Twice what the filters are rated for (ie: a Fluval FX4 for a 125-gallon tank) is a good place to start. You’re not worried about high flow rates with these fish.
- Stop dosing fertilizers and other possible nitrate sources for a few days to weeks and see what happens to the levels.
Higher levels aren’t deadly in and of themselves, but they can lead to the fish becoming ill. Most fish illness ends up being terminal, and these tight-shoaling fish will spread it amongst the entire school very quickly.
These fish will readily take anything you give them. As they get larger you should switch to pellets, as feeding large amounts of flake is a pain.
They’ll get the food, trust me on that one.
That said, in a community tank you may need to take measures to make sure all of your fish and other fauna get fed. Sucking the food into a turkey baster and shooting it into the bottom is a great way to make sure that your bottom feeders stay fed despite the competition.
I prefer to feed most of my larger fish better food at least twice a week, sometimes more. Bloodworms are my go-to, but you can also feed beef heart cubes, brine shrimp, and other frozen foods.
Live foods are usually ideal, but the Roseline Shark doesn’t spend enough time on the bottom to make feeding live worms efficient. Live brine shrimp, juvenile Dwarf Shrimp, and Ghost Shrimp are good choices if you want to encourage their natural hunting behavior.
How Many Roseline Sharks Per Tank?
Roseline Sharks should be in a group as big as you can reasonably manage. A 55-gallon tank is usually enough to host 6 of the species, but that’s the bare minimum for keeping them healthy. Roseline Sharks are very social with their own species.
Roseline Shark Diseases
The best way to avoid problems with these fish getting sick is to follow standard quarantine procedures and make sure that your water is very clean. Lower nitrates is the best indicator for the most part.
That said, you may still have to deal with the diseases these fish can catch. Some are fatal in all cases, some can be cured. Most require you to treat the tank, even if the only fish you saw catch it is already dead.
For our fish, we have a few sources of disease. Parasites, like the well-known ich, require different treatment than bacterial infections. Likewise, fungal infections should be handled with different medications than those used for bacterial issues.
Any fish which is faded in color is stressed and at risk of catching a disease. There’s a reason that experienced keepers insist on such low nitrates.
Of course, there are viruses too but these diseases are rarer and there’s not a whole lot you can do about them.
If you’re not familiar with the common signs and symptoms of fish becoming ill you should acquaint yourself with the most common diseases. They include the following:
- Ich- A parasitic infection that appears as white dots on the fish, often clustered around the gills. Ich can kill a fish if allowed to progress but can be cured by raising the water temperature and adding a bit of salt. Can also be treated with antiparasitic formulas if there are tank mates incapable of tolerating salinity.
- Fin Rot- Fin rot shows as tearing at the edge of the fins that continues to spread over time. Fin nipping or other injuries often produce it, but at times it appears almost spontaneous. Treat as a bacterial infection.
- Dropsy- The fish will appear bloated, often with bulging eyes. Unfortunately, dropsy is generally a fatal symptom. I say symptom instead of disease because the cause can be anything from fungal infections to liver failure. Bloat also falls into this category.
- Cotton Mouth Disease- Manifests as a cotton-like growth on the fish’s mouth. It’s usually bacterial in the cause, but can easily be confused for a fungal infection. Treat with antibiotics initially if the disease is only showing up on the mouth.
- General Fungal Infections- Fungals usually show up as growths on the fish’s body that resemble patches of fuzz. Quarantine the fish and treat both tanks to avoid spread. In my experience, fungal infections are most often seen on injured fish and controlling spread is as easy as adding an antifungal. The fish showing symptoms initially should be monitored and euthanized if necessary.
- General Bacterial Infections- There are hundreds of bacteria that can infect fish. The results range from red sores to streaks of color to bloating. Bacterial infections should be countered with broad-spectrum antibiotics and any fish showing symptoms should be quarantined.
The main problem with treating fish is that most of us aren’t fish-specialized veterinarians. We’re often left guessing and hoping that we have the right cause.
In all cases, treatment should involve treating the display tank, quarantining any fish showing symptoms, and treating them separately.
Roseline Sharks are prone to ich infections. Ich is among the most easily identified and treated fish diseases. Adding some salt and a few degrees of raised temperature until the infection has run its course has a high success rate when caught early.
Don’t add salt directly, instead mix it into another bucket and create brine to add to the tank. 2 teaspoons per gallon of water in the tank will take care of it, and the salt will be diluted and removed naturally during future water changes.
I recommend keeping medications on hand, especially with fish that are prone to diseases. An antibacterial solution and an antifungal medication should both be in your aquarium’s supplies.
Humane Euthanasia for Fish
There are times when it’s kinder to put down an ill fish than it is to let them continue to suffer. In the case of advanced bloating, with a distended abdomen, or infections that won’t budge while the fish’s condition deteriorates you may have to act.
Clove oil is used as an anesthetic for fish, but at a higher dose, it’s the kindest readily-available way to euthanize fish.
- Siphon water from the tank into a spare bucket, preferably one not used on a regular basis for the aquarium.
- Add .5mL of clove oil per liter of water.
- Wait 30-45 minutes, when the fish’s gills have stopped moving for 5-10 minutes then it’s over and you can dispose of the fish in your own fashion.
This is my preferred method for euthanizing fish and causes no distress. In layman’s terms, you’re simply putting the poor little fish to sleep.
Clove oil is readily available in most places. I have a small bottle on hand just in case, since speed is of the essence when it comes to being humane. If the fish has no chance of recovering, then it’s much better to euthanize it than continue to let it suffer until it dies.
Roseline Sharks are compatible with most fish. The problem is that a lot of fish aren’t quite compatible with the Sharks. Their larger size and constant activity can cause stress for a lot of the less high-energy inhabitants in a tank, even if the Sharks don’t interact with them.
The only common fish which are a threat to Denison Barbs are cichlids. Avoid mixing any of the larger species (ie: Oscar, Jack Dempsey) with them. They may not be able to catch and kill the barbs, but they can chase and stress them. Stress fish are prone to disease, which is a major killer for this species.
While peaceful, Roseline Sharks will still take a swipe at smaller fish with longer fins at times. This means fish like Betta, Angelfish, and Guppies are a poor choice for companions. They may not get eaten, but they can certainly become ill after being stressed and injured.
Instead, look for bottom dwellers or schooling fish in the 2 ½-4” range. Some appropriate options include:
- Corydoras Catfish
- Cardinal Tetra
- Gourami (except Sparkling Gourami)
- Harlequin Rasbora
- Tiger Barbs
- Cherry Barbs
- Giant Danio
- Zebra Danio
- Dwarf Cichlids (under 4 ½”)
I’d avoid housing oddballs like eel or bichir with a school of Roseline Shark. Focus on fish that are naturally found in rapid waters and known to be peaceful. Many of the armored catfish, for instance, come from rapids naturally and will be right at home in a tank with the higher flow rate required for Roseline Sharks.
One interesting addition could be a Bamboo Shrimp. Bamboo Shrimp require a high flow and you’ll often find them waving their “fans” at a filter’s output. The high flow rate helps them find more food and they’re large enough to avoid being eaten.
Most smaller shrimp species are going to end up as snacks for Denison Barbs, so be careful what else you add.
These fish are fast enough that you can house them with crayfish or crabs without any risk, but consider any other community inhabitants before you add them.
Breeding Roseline Sharks
Breeding Roseline Sharks at home has happened, but I’ve never heard of it being done intentionally. The few cases of them spawning, and the fact they can spawn in commercial situations, do have a few things we can infer.
The groups which have spawned are always larger in size. Most of them were in very large tanks housing 20 or more fish, with the low end being about 15. This indicated that spawning is something of a group activity, and it’s unlikely to happen at home.
Commercial breeding also uses the addition of hormones to stimulate the breeding impulse. I don’t recommend trying that one at home, even if you’re able to identify and source the needed hormones.
The commercial operations are usually lightly planted and have softer water than the general range for the Roseline Sharks. The individual fish will also have far more space than available in home aquariums. Considering the expansive space requirements already in place for these fish, mimicking these setups at home is a fool’s errand.
So, while they’re endangered there also doesn’t appear to be a way to simulate the environment used commercially at home. Things constantly change in the world of tropical fish, and a better way may be developed, but at the moment any at-home breeding of Roseline Sharks is anecdotal at best.
Fast Flow, Big Space, Tons of Fun
The Roseline Shark isn’t the easiest species to keep, but even a newbie can put together a tank well-suited for them. You’ll need big schools, low nitrates, and fast flow in the aquarium. For the most part, Roseline Shark care can be boiled down to clean, fast-moving water with the rest being minor details.
So, are you ready to start your exciting adventure with these beautiful fish?