Spiny Head Hillstream Loach (Gastromyzon ctenocephalus)

Common Name

Spiney-headed Hillstream Loach, Blue Tail Polka Dot Hillstream Loach 

Origin and Habitat

Native to Borneo, this species thrives in clear, cool forest streams that rush over rounded stones and bedrock. Water is highly oxygenated, flow is strong, and substrates are a mix of larger gravel, cobble, and flat stones with pockets of sand. The rock faces grow a living carpet of diatoms, green film, and micro invertebrates. These fish cling to stone, graze in riffles, and slip into cracks when startled.

Temperature and Water Conditions

Preferred temperature is 68 to 75 F, which is 20 to 24 C. Keep pH near neutral with low to moderate hardness. Stable conditions are far more important than chasing a single number, except for specific breeding projects. Prioritize very high oxygen, mature filtration, and strong directional current. A river manifold or multiple powerheads along a long tank works beautifully.

Appearance and Size

A streamlined hillstream loach with a flattened belly, enlarged fins that act like a suction disc, and a compact, expressive face. Pattern varies by locality, usually olive to chocolate with pale speckling or bars, and clean spotting in the dorsal and tail. Males may show slightly crisper markings and slimmer bodies, females become rounder when full of eggs. Maximum length is about 6 cm, which is roughly 2.4 inches.

Diet in the Wild

An aufwuchs specialist that scrapes diatoms, soft green algae, biofilm, and the tiny invertebrates living in that film. Constant grazing fuels steady energy in fast water.

Feeding in Captivity

Build a menu that mimics a living stream bed. Offer spirulina and herbivore wafers, quality grazer pellets, and gel foods. Supplement with blanched vegetables such as zucchini coins or spinach, and small frozen items like daphnia, cyclops, and baby brine shrimp as a treat. The best hack is to grow your own rocks. Keep a bucket or shallow tub under bright light with smooth pebbles so they grow real biofilm, then rotate those stones into the tank. Feed small amounts two or three times daily so food never rots in high flow.

Behavior and Tank Setup

Peaceful and social. Keep a group of six or more so you see relaxed grazing and short sprints between stones. Use a long footprint tank with strong current, abundant oxygen, and plenty of smooth rock. Larger gravel, rounded river stones, and a few flat slate pieces make ideal perches. Plants are optional. Anubias, river mosses, and bolbitis tied to stone look great and do not mind the current. Choose tank mates that love cool, fast water and ignore algae grazers, such as Sewellia, other Gastromyzon, small Garra, danios, and white clouds. Keep a tight lid since these fish can climb glass at the surface.

Breeding

Conditioning: Keep water pristine with high oxygen and strong current. Condition a group on biofilm rocks and small daily feedings of quality prepared foods. Rotate algae covered stones from your grow tub so natural graze is always available.

Spawning cues: Spawning often follows heavy feeding and cool, fresh water changes that mimic rains. Courtship is subtle. You may not see the act, only the results.

Rock piles and larger gravel: Build several rock piles over a base layer of larger gravel. The gaps between the larger gravel form a fry zone where eggs roll down out of reach. Direct a steady current across the top of each pile so eggs drift and settle into the gravel lattice. This structure also traps biofilm and micro life for the fry.

Egg handling: If you want to maximize yield, lift the top stones from one pile every few days and gently swirl water through the gaps to dislodge eggs and early wigglers into a floating breeder box with coarse mesh. Keep pre filter sponges on all inlets and keep oxygen very high.

Raising fry: Fry are tiny and benthic. The larger gravel matrix and rock piles are their pantry and shelter. Do not vacuum the fry zone during the first weeks. Rotate in algae covered pebbles often. You can paint small stones with a thin slurry of powdered spirulina and tank water, let them dry, then place them where fry hide so they can graze safely. After the first week begin offering very fine powdered foods and tiny portions of newly hatched brine shrimp downstream of the piles so the current delivers food through the gaps. Perform small daily water changes, keep temperature steady in the cool range, and maintain intense aeration. Growth is steady, and within a month you will see miniature grazers on open stone.

Quick Facts

• Scientific name: Gastromyzon ctenocephalus
• Common name: Spiny Head Hillstream Loach
• Origin: Borneo forest streams with fast, clear, highly oxygenated water
• Adult size: about 6 cm, roughly 2.4 inches
• Temperature: 68 to 75 F preferred
• Wild pH: near neutral, low to moderate hardness
• Temperament: peaceful grazer, best in a group
• Diet: biofilm, diatoms, soft algae, tiny invertebrates, accepts spirulina based prepared foods
• Breeding type: egg scatterer among stones, eggs and fry develop in rock piles over larger gravel

Tropical Fish Co. Notes

These fish are tiny hovercrafts with huge personalities. When they are happy, they patrol the current like little flying saucers and the spots glow under good light. Success is simple. Cool, clean, fast water. Smooth stones in heaps over a layer of larger gravel. Real biofilm to graze, whether grown in the tank or rotated from a sunny tub. Keep parameters steady, give them a river to ride, and if you are breeding, let the rock piles and gravel lattice do the work for you.