How to keep hillstream and brook loaches in the aquarium


Emma Turner on hillstream and brook loaches — fish that have to overcome every water condition nature cares to throw at them.

Hillstream and brook loaches are highly modified bottom dwellers enduring incredibly difficult environments.

These can range from from oxygen-rich, swift, cool mountain streams to torrential rivers and rapids with water hurtling along at more than 3m/10’ per second!

Why then do so many retailers treat these fish so poorly?

All too often these evolutionary masterpieces are dumped in relatively slow-moving waters of a typical goldfish system, and wrongly labelled as "coldwater algae eaters", "Hong Kong plecs" and "dwarf weather loaches".

Here they will be incredibly unhappy, often clamping down their fins while slowly suffocating.

These fish are Cypriniformes and the Cobitoidea (loach fish) super family within the order is further split into eight — two being Balitoridae and Nemacheilidae.The Balitoridae family contains more than 30 genera, many being seasonally seen in the trade. The more common include Annamia, Gastromyzon, Homaloptera, Pseudogastromyzon, and the recently popular Sewellia.

Such shoddy treatment in our shops is particularly distressing for the balitorid species and many retailers appear to act this way simply because their stocks are sold so quickly, often to unwary aquarists more than likely unprepared for the specialised conditions these fish require.

Hillstream loaches, with their highly adapted streamlined shapes, live in the temperate waters of fast-flowing streams, rivers, and rapids across the Indian subcontinent, South-East Asia, China, and parts of Eurasia.

They possess modified pectoral and pelvic fins, creating a powerful suction cup that enables them to cling on, crawl along and eat from the surfaces of rocks in high-velocity rapids.

Brook loaches inhabit a slightly less harsh niche; cool oxygen-rich mountain streams of fast current and shallow depths.

These torpedo-shaped fish are from a widespread family, distributed across Eurasia, the Indian subcontinent, South-East Asia, and China.

Once grouped with the Balitoridae, Nemacheilidae was first recognised as a genetically distinct group in 2006. It includes some aquarium favourites such as Aborichthys, Acanthocobitis, Mesonoemacheilus, Nemacheilus, Schistura and Yunnanilus.

Schistura is the most diverse genus in Nemacheilidae, consisting of almost 190 species of which more than 100 have been described since 1990!

Preparing your tank for these fish

These fish will not thrive — in some cases, be able to live — in a standard community aquarium. Their tank must be set up quite differently; namely with cooler water, extreme high flow (uni-directional if possible) and high level of oxygenation.

Powerful filtration provided by external canisters with spray bar return/s and additional powerheads can ensure adequate flow and oxygenation, but a more effective method would be to install a piece of kit known as the 'river tank manifold'.

Ideally the tank will be quite long but not too tall, and something along the lines of 122 x 38 x 46cm/48 x 15 x 18" is fine. You certainly wouldn’t want anything shorter than 36"/91cm.

Before adding any décor, the manifold must be constructed. It’s not difficult to assemble and not overly expensive either.

Water is drawn in at one end via the intake sponge filters, through the tubing, hidden under your substrate, and blasted back across the tank in one direction by the powerheads. This process is continually repeating, creating the powerful uni-directional flow primarily encountered by these fish in natural surroundings.

Simply adding powerheads, while obviously beneficial to the fish, will impart a tumbling action to the water and not what we are striving to create. Long term, this may not serve the fish as well as it could.

You’ll need to source some 20mm rigid plastic pipework from an aquatics shop, along with 90° elbows and T-pieces to fit. Some DIY stores carry such items for portable water supplies.

The length of tubing required will depend on your aquarium. When fitted together, the whole manifold wants to reach from one end to the other. Some drilled tubing, plus small pond filter sponges can be used for the intake end.

Improvisation may be needed when fitting the powerheads to the manifold. However, manufacturers such as Maxi-Jet supply powerheads with rigid stepped intake tubes that can be pushed directly into the upright T-pieces.

The manifold must be glued together before use, with aquarium-safe adhesive, such as Tangit solvent-weld glue — again something a good store should be able to order in. This product dries in 30 seconds, so everything must be cut to size and assembled together — making sure everything fits accurately — before sticking it permanently.

Turnover rate

Make marks on the correctly assembled pipework and fittings with a pen prior to gluing. This ensures that everything meets precisely wthin your limited time.

The size of powerheads required will be determined by the size of the aquarium, but aim for a total turnover rate of at least ten times per hour. The longer the aquarium, the more effective the uni-directional flow. The middle struts of the manifold, while also returning water to the powerheads, help ensure that the structure is supported and held securely with your substrate and décor.

Without a central strut, it’s difficult to anchor the manifold adequately, so it should not be left out. For wider tanks, the manifold can be adapted to take more powerheads and further central struts.

Although a lot of beneficial bacteria will colonise the sponges on the manifold, combine this equipment with external filtration for added water movement/oxygenation/removal of nitrogenous wastes. Position the spray bar on the side of the aquarium at the powerhead end and place the filter intake tube at the same end as the sponges.

Additionally, by running a slightly dropped water level and positioning the spray bar above it, the returning filtered water will splash on the surface, therefore maximising oxygenation.

While ball-shaped ‘stream’ circulation pumps provide exceptional flow, don’t add these to a tank of hillstreams. The fish, some with a particularly wide, flat ventral surface and reduced ability to swim in open water, can be easily pulled onto the surface of the cage surrounding the impeller and find it impossible to get off.

Once the manifold is in position, slowly add your pre-rinsed substrate, ensuring the pipework is hidden. River beds tend to consist of a variety of substrates: differing sizes of rocks/cobbles are worn by the unrelenting current, forming small rocks, smooth gravel and sand. I prefer sand in all of my loach aquaria, but a mix of substrates can be more natural. Any gravel that feels sharp can damage bottom-dwelling fish.

Larger smooth boulders and cobbles can be added, and placing them over the top of where you know some manifold struts are is the best option as this ensures everything is weighted down.

Choose smooth/flat décor to resemble water-worn rocks. Driftwood may also be added, but ensure the path of the flow from the powerheads is not excessively interrupted as this will interfere with the uni-directional current.

Plants may be added, but not all species fare well under such conditions. These fish don’t encounter much plant life in the wild, but greenery can make the tank more aesthetically pleasing.

Robust species that have done well include Anubias and Microsorum (Java fern), which can be anchored to the décor above where the flow is most intense. Some aquarists have also been successful with Java moss (Taxiphyllum barbieri), but this needs to be tied securely on to the décor and again away from the fastest flow.

Add fertiliser

I have grown Cryptocoryne crispatula var. balansae in many river tanks and these have always done exceptionally well, even when planted in full flow of the current. A little root fertiliser placed between the struts of the manifold, before adding substrate over the top, can be very beneficial too.

Temperature is best maintained within 18-25°C/65-77°F.  Any higher and oxygen levels start to become depleted and your hillstream/brook loaches may become uncomfortable.

Some species have coped with spells of higher temperatures, for instance during a hot summer, but this should not be the norm.

Air stones can be added to further boost oxygen levels and they represent a handy back-up should the temperature rise unusually high.

Lighting should be bright to encourage algae growth on the rocks and cobbles — a food which balitorid species enjoy grazing upon for the organisms it contains.

Introducing your fish

As hillstream and many brook loaches can be delicate when first imported, they must be added only to mature aquaria and, even then, only after your dealer has rested them in suitable conditions.

Once your tank has cycled, start stocking with small ‘dither fish’ that will enjoy the fast flow and lower temperature.

Some of the smaller danios, rasbora, and barbs make ideal candidates for this role as do the mountain minnows and other coolwater cyprinids such as species of Barilius.

Glowlight danio (Danio choprae), Kyathit danio (Danio kyathit) and the Vietnamese mountain minnow (Tanichthys micagemmae) make beautiful additions and will complement the loaches superbly.


Hillstream loaches need a varied diet. They will naturally browse on benthic algae that contains aufwuchs, but supplement this with such as cucumber, courgette, blanched spinach, plus meaty foods such as bloodworm, white mosquito larvae, vitamin-enriched brineshrimp, Daphnia and small sinking pellet foods.

You should only wipe the front glass of your tank, letting algae freely colonise the sides and back.

Exact water parameters will depend on the species. Some are from soft acidic blackwaters in the rainforest, others from more neutral conditions or the hard alkaline waters that channel their way through limestone mountains.

Partial water changes should be carried out ideally twice a week.

Nitrates must not be allowed to build up in your set-up, as these wild-caught loaches are used to the fresh waters their natural habitats constantly provide and therefore are intolerant to any build-up of organic wastes.


Hillstream and brook loaches are fascinating creatures.

Most are quite peaceful, although will sometimes defend territories, particularly when food is involved, against conspecifics.

Males of the Gastromyzon and Pseudogastromyzon genera sometimes get involved with some scuffling behaviour, flashing their exquisite tails and dorsal fins at one another, but actual harm rarely occurs as result.

Sewellia species can be pushy, 'topping' one another like stingrays. Other balitorids, such as Annamia, Beaufortia, and Homaloptera will make peaceful additions.

Take care with certain brook loaches, as many of the Schistura and Nemacheilus species can be aggressive, particularly towards their own kind.

Larger tanks with visual barriers among the décor are key to harmony with these.

Other genera, such as Traccatichthys (formerly Micronemacheilus) contain some of the most sociable brook loaches in the hobby.

Can I breed some of these species?

A handful of enthusiasts have successfully bred a few delightful hillstream species, namely Pseudogastromyzon cheni, P. fangi, Liniparhomaloptera disparis disparis, Sewellia lineolata, Sewellia sp. 'spotted' and Homaloptera confuzona.

Quite a number of brook loaches have also been bred under river tank conditions, including Mesonoemacheilus triangularis, Acanthocobitis botia, Schistura cf. balteata, and S. nicholsi.

Most success stories occur predominantly in species-only aquaria where there’s little predation on eggs or fry. A number of youngsters have also been found in external canister filters running on river tanks, after the fertilised eggs have been sucked into the inlet, and gone on to develop in the relative safety of the media chambers.

Check the contents of yours during routine maintenance!

Guide to the species

Some of the more commonly seen balitorid and nemacheilid species in the trade include:

Borneo sucker (Gastromyzon ctenocephalus)

This beautiful balitorid is of a handful of species regularly imported as the Borneo sucker.

Kept under correct conditions, these will be highly active and show wonderful flashes of bright blue on the dorsal and caudal fins.

G. scitulus looks very similar, but the two can be told apart by the blue dorsal markings on G. ctenocephalus (absent in G. scitulus), blue in the caudal fin of G. ctenocephalus broken by thin horizontal black stripes (blue in the caudal broken by both black bars and horizontals, giving a stained glass appearance in G. scitulus), smaller spots along the back and flanks (against larger spots less densely distributed in G. scitulus), plus such as fin rays counts.

Maximum size: 5cm/2”.

"Hong Kong plec" (Pseudogastromyzon cheni)

This balitorid species, known from the Hanjiang river drainage of Fujian province, China, is traded fairly frequently — and it is probably the most abused of the fast flowing, oxygen-rich water loving family in terms of being housed incorrectly.

Healthy and happy specimens, however, will be energetic and actively flashing their distinctive pillar-box red dorsal fins.  This is one of the easiest loaches to breed and spawning behaviour is simply fascinating to observe.

Maximum size: 6cm/2.4”.

Gold ring butterfly sucker (Sewellia lineolata)

Native to central Vietnam, this is one of the most attractive balitorids with a striking gold and black colour pattern, coupled with bold behaviour.

Easy to breed, fry undergo dramatic pattern and colour changes as they grow. As they are exceptionally confident, sometimes pushy, at feeding times ensure more placid fish are not missing out.

Intraspecific dominance battles, more showy than damaging, are particularly interesting.

Maximum size: 6.5cm/2.6”.

Tri band sumo loach (Schistura cf. balteata)

This flamboyantly coloured species is awaiting description, but readily available. It has been collected from the headwaters of the Ataran drainage flowing through Kayin in Myanmar, formerly Burma, and also from western Thailand, close to Myanmar.

Provide ample visual barriers to ensure any aggression is spread throughout your group and don’t house with any placid species.

Despite some belligerence this is a shy loach and may spend much of the day in small dark crevices. Dither fish will encourage them out into the open more readily.

Markings and patterns are variable and two colour forms (pink and yellow) exist sympatrically in the wild.

Maximum size: 7.5cm/3”.

Red lizard loach (Homaloptera confuzona)

This is the most commonly traded member of a complex of similar looking species separated by the shape of the scale keels.

This elongate balitorid is known from the Mekong river basin downstream of the Khone waterfalls in southern Laos, near Cambodia, and also from smaller coastal river drainages in southern Thailand, including parts of the Mae Klong system.

Provide these fish with water saturated with oxygen and a formidable current.

Homaloptera species are micro-predators darting from a resting place to snatch a morsel of meaty frozen food in relentless currents, then returning in the blink of an eye.

Maximum size: 7.5cm/3”.

Zodiac loach (Mesonoemacheilus triangularis)

This feisty nemacheilid is known from Kerala and Tamil Nadu in India, and is the most regularly traded member of the genus.

Juveniles of this species often sport an eye-catching herringbone or chevron type pattern on the flanks, but markings in general are highly variable.

Some imported batches have turned out to actually be the equally appealing M. guentheri which has an attractive spotted pattern, so check your dealer’s tanks carefully to avoid confusion and a possible mistaken purchase on your part.

When setting up an aquarium for these create an abundance of visual barriers and hidey-holes to reduce aggression levels.

Maximum size: 7.5cm/3”.

Red tailed squirrel loach (Aborichthys elongatus)

This vermiform species is from the cool, shallow, fast mountain streams of North-Eastern India.

Females should be larger and plumper, with males showing brighter colouration, particularly on the concentric red rings on the caudal fin.

It likes to dig and can undermine aquarium décor, so ensure structures are secure.

Specimens may squabble, so ensure plenty of visual barriers/hiding places — and they can’t be trusted with long-finned fish.

Maximum size: 7.5cm/3”.

Zipper loach (Acanthocobitis botia)

This readily available nemacheilid is great for beginners, being relatively hardy and peaceful.

It has a quite a widespread distribution, from the Indus basin in Pakistan to the Mae Khlong basin in Thailand through the Ganges, Chindwin, Irrawaddy, Sitang and Salween basins — and also from Yunnan, China.

However, the vast majority of Zipper loaches seen in the trade are from India and some populations may later turn out to represent separate species.

Maximum size: 11cm/4.3”.

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