Blue dorsal Borneo sucker
Gastromyzon ctenocephalus
The blue dorsal Borneo sucker features a distinctive blue dorsal fin, elongated body, and a flattened head, adapted for life in fast-flowing waters.
This page includes AI-generated images. Why am I seeing AI images?
About the Blue dorsal Borneo sucker
This is one of the little Borneo hillstream loaches that scoots around like a tiny living suction cup, spending most of its day grazing on biofilm off smooth rocks. The cool part is the fin patterning - the caudal fin has bold pale-blue striping, and they do those quick little territorial "flaring" displays with each other without usually doing real damage. Keep it in a high-oxygen, high-flow setup and it just settles in and does its thing.
Also known as
Quick Facts
Size
4.5 cm SL
Temperament
Peaceful
Difficulty
Intermediate
Min Tank Size
12 gallons
Lifespan
3-6 years
Origin
Southeast Asia (Borneo)
Diet
Omnivore-grazer - biofilm/algae plus sinking foods, wafers, and small frozen/live foods
Water Parameters
20-23.8°C
7-8
8-12 dGH
Need a heater for this species?
This species needs 20-23.8°C in a 12 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give them a long tank with a hard current - powerhead or strong filter return aimed down the length, plus smooth river stones and a few pieces of driftwood to break up flow.
- Keep the water cool-ish and oxygen-packed: 68-75F is the happy zone, and they sulk fast in warm, stagnant water; lots of surface agitation is your friend.
- They are algae grazers, but they do better if you feed on purpose: rotate algae wafers, Repashy Soilent Green, blanched zucchini/spinach, and small frozen foods like baby brine or daphnia.
- Set up real grazing surfaces (rounded rocks, slate, wood) and let some biofilm grow; a spotless new tank is basically an empty fridge for them.
- Pick tankmates that like current and wont hassle them - small danios, white clouds, hillstream loaches; avoid fin-nippers, big cichlids, and pushy bottom fish that camp on their rocks.
- Watch for them getting outcompeted at feeding time since they stick to surfaces and dont dash to the front; I drop food right onto their favorite rocks after lights out.
- Common fail: too little flow and too much heat equals skinny fish and sudden losses; if you see rapid breathing or they leave the glass/rocks to hover, crank up aeration and check ammonia/nitrite right away.
- Breeding happens in mature, high-flow setups with lots of crevices - pairs will wedge under rocks and scatter eggs; dont expect a big spawn, but you might spot tiny fry grazing biofilm if you dont over-clean.
Compatibility
Good Tankmates
- Hillstream-type buddies like other Gastromyzon or Sewellia (keep a small group, lots of rocks and flow so they can do their little shoving matches without stressing anyone)
- Small, peaceful midwater fish that like cooler, fast, oxygen-rich water - think white cloud mountain minnows
- Danios (zebra, pearl, etc.) - active but usually not mean, and they love the current so everybody is in the right kind of setup
- Rasboras that can handle flow like harlequins or lambchops - they stay out of the suckers' way and dont mess with the perches
- Small, chill loaches like kuhli loaches (as long as you still have plenty of smooth rock surface and they are not competing for the same exact 'prime' spots)
- Nerite snails or Amano shrimp - generally safe, and they fit the whole algae-grazer vibe without bothering the suckers
Avoid
- Big aggressive or predatory fish like cichlids (most), larger barbs, or anything that sees a flat little fish on a rock as a snack or a target
- Nippy fin-biters like tiger barbs - they dont always go after the sucker, but the constant harassment and chaos stresses them out in a high-flow tank
- Cold-to-warm mismatch fish like bettas or most fancy guppies - they hate the strong current, and the warmer, calmer setup they want is basically the opposite of what Gastromyzon thrives in
- Big, pushy bottom claimers like many common plecos or large Botia loaches - they hog food, shove everybody off the rocks, and the sucker loses out long term
Where they come from
Blue dorsal Borneo suckers (Gastromyzon ctenocephalus) come from fast, cool(ish) hill streams in Borneo. Think clear water, lots of oxygen, rock piles, and a steady push of current. If you set up your tank to feel like that, the fish pretty much does the rest.
These are river-hillstream loaches, not algae-eaters for a calm community tank. They can live in a normal aquarium, but they act and feed like a fish built for rapids.
Setting up their tank
The tank is 90% of success with this species. They want high flow, high oxygen, and lots of hard surfaces to graze. I have had the best results in a long tank (more footprint beats more height) with a powerhead aimed down the length to make a clear "river lane".
- Tank size: 20 gallons long minimum for a small group, bigger is nicer because flow is easier to spread out
- Flow: strong, but give them rest spots behind rocks and wood where the current breaks
- Filtration: oversized and clean - these fish hate stale water
- Oxygen: surface agitation matters; a powerhead rippling the surface does a lot
- Substrate and hardscape: rounded river stones, smooth cobbles, and some flat rocks for grazing; sand or fine gravel underneath is fine
- Plants: optional; if you use them, stick to stuff that can handle current (Anubias, Java fern, Bolbitis) tied to rocks/wood
Make at least one flat "feeding rock" that sits in good flow. Mine learned to camp there because food and biofilm keep landing on it.
Water parameters do not need to be weird, just stable and clean. Neutral-ish pH is fine. I keep them in the low-to-mid 70s F, and I avoid warm, sluggish setups. Regular water changes go a long way because they are sensitive to gunk building up.
Avoid freshly set up tanks. A new tank with squeaky-clean rocks usually means not much natural grazing. Let the tank mature or seed it with algae/biofilm from an established system.
What to feed them
They graze all day. You will see them vacuuming rocks like little living suction cups, and that biofilm is part of their diet. The mistake people make is thinking they can live on whatever algae shows up on the glass. They need real food, and they do better with variety.
- Staples: sinking wafers that are heavy on algae/spirulina, and high-quality bottom-feeder pellets
- Veggies: blanched zucchini, cucumber, spinach, or green beans (remove leftovers before they mush)
- Protein a few times a week: frozen bloodworms, daphnia, brine shrimp, or small sinking meaty pellets
- Grazing help: let some rocks get a light fuzz of green, and do not scrub everything spotless
Feed after lights out sometimes. In a busy tank, shyer individuals will wait until the commotion dies down, and you will get a more even body condition across the group.
How they behave and who they get along with
They are peaceful, but they are not pushovers. You will see little shoving matches and "parking disputes" over the best rocks, especially between similar-looking hillstream fish. It is usually all bluff and posturing, not damage.
I strongly prefer keeping them in a small group. In singles, they can get withdrawn and you miss a lot of their normal behavior. In groups, they spread out, graze more confidently, and the minor squabbles stay minor because no single fish owns the whole tank.
- Good tankmates: small, current-loving fish like danios, white cloud mountain minnows, some rasboras, and peaceful loaches that like similar water movement
- Also works: shrimp and snails (they generally ignore them)
- Avoid: slow, long-finned fish that hate flow (bettas, fancy guppies), big boisterous bottom-feeders, and aggressive territory hogs
- Be careful with: other hillstream loaches if the tank is small - crowding increases the "rock wars"
They can lose out at feeding time if you keep them with fast, greedy eaters. Watch their bellies. A well-fed Gastromyzon looks nicely rounded from above, not pinched.
Breeding tips
Breeding in home tanks can happen, but it is not something I would count on quickly. The best "breeding tip" is really just giving them a mature, high-flow setup with lots of hiding cracks and stable water quality. If they do spawn, the eggs and fry are tiny and easy to miss.
- Keep a group with both sexes (sexing is subtle; a group gives you better odds)
- Lots of crevices under stones and between rounded rocks
- Heavy feeding plus frequent water changes can trigger activity
- If you suspect fry: add gentle sponge filtration and offer powdered foods, infusoria, and biofilm-rich surfaces
If you ever spot miniature versions clinging to the glass or rocks, do not suddenly deep-clean the tank. The micro-life and film on surfaces is basically their buffet.
Common problems to watch for
Most problems with this species trace back to low oxygen, not enough flow, or not enough food. They are tough once settled, but they do not love being shipped, bounced between tanks, and dropped into a brand new setup.
- Starvation: hollow belly, lethargy, hanging in one spot without grazing (common in new tanks with little biofilm)
- Low oxygen/high waste: rapid breathing, staying near the filter outflow, acting "off" after a missed water change
- Getting outcompeted: they look fine at first, then slowly thin out in a tank with aggressive feeders
- Ich and stress spots after purchase: happens if they are chilled or stressed in transport
- Injuries from sharp decor: scraped bellies and fins if you use jagged rocks
Do not medicate casually. Many loach-type fish can react badly to strong doses, especially copper-heavy meds. If you have to treat, research the medication and start gentle.
My routine for keeping them trouble-free is simple: strong current, lots of oxygen, mature rocks to graze, and consistent feeding. If you do those four things, Blue dorsal Borneo suckers are one of the coolest "always doing something" fish you can keep.
Similar Species
Other freshwater peaceful species you might be interested in.
Aboina barb
Enteromius aboinensis
Enteromius aboinensis (the Aboina barb) is a small West African barb with a clean black midline stripe and a little spot right at the base of the tail. It does best when you treat it like a proper schooling fish - keep a decent group and give it plants around the edges with open swimming room in the middle.
Ajuricaba tetra
Jupiaba ajuricaba
Jupiaba ajuricaba is a South American freshwater characin from the Amazon basin in Brazil (rio Negro, rio Solimões, and rio Tapajós basins). It reaches about 9.5 cm SL and is diagnosed by a narrow dark midlateral stripe, an elongated humeral spot, and an ocellated spot on the upper caudal-fin lobe. Wild specimens have been collected from blackwater forest streams and also oxbow-lake habitats.
Allen's river garfish
Zenarchopterus alleni
A poorly known freshwater halfbeak endemic to West Papua (Mamberamo River), described from a single specimen (~13 cm SL). Beyond basic habitat/occurrence, little is published about its ecology or aquarium suitability; assume it is a surface-oriented, jump-prone halfbeak only by analogy with related taxa.
Amapa tetra
Hyphessobrycon amapaensis
This is a tiny, super sleek little tetra with a clean red stripe down the side that really pops once its settled in. It does best in a planted, slightly tinted "creek-style" setup and looks way cooler when you keep a proper group so they school and flash that line together. If you can give it soft, slightly acidic water and a calm community, its an easy fish to fall for.
Amatlan chub
Yuriria amatlana
Yuriria amatlana (the Amatlan chub) is a little Mexican native minnow from the Ameca River basin. Its wild range is pretty limited and it is listed as Endangered, so its care info in the aquarium hobby is basically nonexistent and its availability is usually low. In the original species description, preserved fish show a dark lateral stripe with a darker patch on the caudal peduncle, and they can have tiny barbels at the mouth corners.
Andrica moenkhausia
Moenkhausia andrica
Moenkhausia andrica is a little Brazilian characin from the Tapajos system that tops out around 7 cm (about 2.8 inches) standard length. It has a neat netted (reticulated) scale pattern plus a dark spot on the caudal peduncle, and the really wild part is that mature females can have tiny fin hooklets too, which is usually a male-only thing in a lot of characins.
More to Explore
Discover more freshwater species.
Altipedunculata stone loach
Schistura altipedunculata
Schistura altipedunculata is one of those little stream loaches that wants clean, well-oxygenated water and a bunch of rock nooks to claim as home. It is a bottom-hugger that will spend its day scooting from crevice to crevice, and it tends to get a bit spicy with its own kind if you do not give it enough hiding spots.
American flagfish
Jordanella floridae
Jordanella floridae is that little Florida native with the red-and-cream striping that really does look like a tiny flag once a male colors up. They graze algae like champs (especially stringy/hair algae), but they have a bit of attitude - give them plants and space so the bossy behavior stays manageable. Bonus: the male guards the eggs and will actively fan them, which is pretty fun to watch.
Amur sculpin
Alpinocottus szanaga
This is a little coldwater sculpin from the Amur drainage - a bottom-hugging, rock-and-gravel fish that spends its day wedged under stones and darting out to grab food. Super cool behavior and attitude, but it is absolutely not a warm tropical community fish - it wants chilly, fast, oxygen-rich water and will bicker with other bottom fish.
Anhanga pygmy pencil catfish
Potamoglanis anhanga
This is a truly tiny Amazonian trichomycterid catfish - like 1.3 cm max - so it is more of a micro-predator oddball than a typical community catfish. It is the kind of fish that disappears into sand, leaf litter, and plant roots, and you will spend way more time setting up the right micro-habitat than you will actually seeing it.
Anitápolis livebearer
Jenynsia weitzmani
Jenynsia weitzmani is a freshwater anablepid livebearer endemic to southern Brazil (currently known only from the type locality near Anitápolis, Santa Catarina). Like other Jenynsia (onesided livebearers), reproduction involves lateralized mating morphology/behavior; aquarium care guidance is not well-documented for this species specifically.
Anteridorsal Homatula loach
Homatula anteridorsalis
This is a benthic Chinese stream loach from Yunnan that lives right down on the bottom in clear, flowing water over gravel and rocks. Think of it as a "river tank" fish - it wants current, oxygen, and lots of surfaces to poke around on for bits of food and algae.
Looking for other species?