---
type: species
title: "Reticulated Hillstream Loach Care: The \"Stingray\" Loach Guide"
slug: "reticulated-hillstream-loach"
category: "freshwater"
scientificName: "Sewellia lineolata"
subcategory: "Loach"
lastUpdated: "2026-04-24"
readingTime: 9
url: https://www.fishstores.org/species/reticulated-hillstream-loach
---

# Reticulated Hillstream Loach Care: The "Stingray" Loach Guide

*Sewellia lineolata*

Master Reticulated Hillstream Loach care. Learn about Sewellia lineolata tank requirements, high-flow setups, algae feeding, and compatible tank mates.

## Species Overview

The reticulated hillstream loach (*Sewellia lineolata*) is the closest most freshwater hobbyists will get to keeping a stingray. Native to the fast, oxygen-saturated streams of central Vietnam, this flat-bodied grazer uses a suction-cup belly and wing-shaped pectoral fins to hold position in current that would knock most aquarium fish sideways. The fine reticulated mesh of dark lines across its olive-and-tan back is what earned it the trade names "reticulated hillstream loach" and "butterfly loach" — and a near-permanent spot on intermediate hobbyist wishlists.

Unlike most species sold under the broad "hillstream loach" umbrella, *Sewellia lineolata* is consistently identifiable by its broad, flattened body and the prominent reticulation pattern that runs from snout to tail. It is the same species covered in our broader [hillstream loach care guide](/species/hillstream-loach) — this guide focuses specifically on the reticulated trade name and the buying decisions that go with it.

| Field       | Value                                    |
| ----------- | ---------------------------------------- |
| Adult size  | 2.5–3 in (6–7.5 cm)                      |
| Lifespan    | 8–10 years                               |
| Min tank    | 20 gallons (long footprint, group of 3+) |
| Temperament | Peaceful, mildly territorial             |
| Difficulty  | Intermediate                             |
| Diet        | Aufwuchs / biofilm grazer                |

### The "Butterfly Loach" Aesthetic: Patterns and Body Shape

The reticulated hillstream's body is a teardrop pancake — wide at the shoulders, narrow through the caudal peduncle, and almost completely flat in profile. Pectoral and pelvic fins flare outward like aircraft wings, generating downforce against the current the way a rear spoiler keeps a race car planted on the road. This is why a smooth river stone or vertical glass surface holds them better than gravel.

The reticulation itself is a fine network of dark lines on a tan or olive base, and it is the easiest way to distinguish *Sewellia lineolata* from the spotted *Gastromyzon* species also sold as butterfly loaches. If you cannot read the reticulation pattern clearly through the store glass, ask the staff to point one out — the "lined" appearance is unmistakable up close.

### Natural Habitat: The High-Oxygen Streams of Vietnam

Wild *Sewellia lineolata* live in the shallow, fast-flowing streams of central Vietnam, mostly in the Quang Nam and Quang Ngai provinces. The water runs over bedrock and rounded cobbles year-round, stays cool thanks to forest canopy and elevation, and rarely sits still long enough for sediment to settle. Dissolved oxygen runs at saturation because the constant turbulence keeps surface gas exchange maxed out.

Their food in this environment is biofilm — the slick green and brown coating of diatoms, microorganisms, and detritus that builds up on every submerged surface. Hillstream loaches are perfectly adapted to scrape it off with their underslung mouths and spend their waking hours in slow, methodical grazing patterns.

### Lifespan and Maximum Size (2.5 to 3 inches)

Reticulated hillstream loaches reach a maximum size of 2.5 to 3 inches, with most aquarium specimens settling around 2.75 inches at maturity. Growth is slow — expect roughly an inch in the first year and full adult size by year three.

In a properly oxygenated, cool tank, healthy specimens routinely live 8 to 10 years. That puts them in the same lifespan bracket as many cichlids, which surprises keepers who buy them as a temporary "algae crew" addition. Plan for a long-term commitment, not a cleanup utility.

## Water Parameters & Tank Requirements

These loaches are not difficult, but they are specific. The equipment choices below are non-negotiable in a way that most community species can forgive.

> **High flow and oxygen are mandatory**
>
> Standard community-tank flow rates will not keep these fish alive long-term. Plan for total tank turnover of 10 to 20 times per hour through dedicated powerheads or a river manifold, plus a primary filter rated well above your tank volume. Low oxygen — almost always caused by inadequate flow or warm water — is the single most common cause of death in home aquariums.

### Simulating the "Hillstream": Powerheads and Manifold Systems

The gold standard is a river manifold — a length of PVC pipe drilled with small holes, connected to a powerhead at one end, and laid horizontally along the back wall just above the substrate. Water shoots out through the holes in a unidirectional sheet, recreating the laminar current of a natural stream. Loaches face into the flow and graze on rocks placed in front of the holes.

A simpler alternative that works almost as well is a pair of small powerheads (Hydor Koralia 240s or similar) mounted at one end of the tank, both pointing the same direction. The water hits the far wall, curves down, and circulates back along the substrate. Aim for 10 to 20 times tank turnover per hour combined across all flow sources, not counting your primary filter.

For a nano build, an all-in-one tank like the [Fluval Flex](/guides/fluval-flex) works as a small footprint platform if you supplement the rear filtration chamber with a small internal powerhead pushing flow across the open display. Just be honest about scale — a 15-gallon Flex caps you at one or two loaches, not a proper group.

### Temperature (68°F–75°F) and the Importance of High Dissolved Oxygen

Target a temperature range of 68 to 75 degrees F. In most heated indoor environments, no heater is needed. If your house drops below 65 in winter, set a heater to the bottom of the range as a safety floor — but never heat into the upper 70s. Temperatures above 78 reduce dissolved oxygen quickly, and the loaches will start gasping at the surface within hours.

Dissolved oxygen is the controlling variable. Cool water holds more oxygen than warm water, and turbulent water holds more than still water. A fish gasping at the surface or sitting permanently on filter outputs is begging for more oxygen, not asking to be moved closer to food. Add air stones, a second powerhead, or both before adjusting anything else.

Ammonia and nitrite must read zero. Nitrate should stay under 20 ppm. Weekly water changes of 25 to 30 percent with cool, dechlorinated water both refresh oxygen and dilute waste.

### Substrate Choices: Smooth River Stones vs. Fine Sand

The natural substrate is fine sand interspersed with smooth, rounded river cobbles ranging from golf-ball to grapefruit size. Reproduce that. Stack a few flat stones on edge to create vertical grazing surfaces, and use sand or very fine gravel as the base layer.

Avoid sharp gravel and lava rock. The flat belly of a reticulated hillstream loach drags across the substrate constantly, and sharp edges cause abrasion that opens the door to bacterial infections. The total grazing surface area you provide directly determines how many loaches the tank can support — a 20-gallon long with a dozen baseball-sized stones can comfortably feed three to five adults from natural biofilm production alone.

### Lighting for Algae Growth (The "Green Wall" Method)

Run brighter and longer lighting than you would for a typical community tank. Eight to ten hours of strong full-spectrum light per day encourages the diatom and green-algae growth that feeds the loaches. The "green wall" method — letting one side panel of the tank grow a thick algae mat unscraped — gives the loaches a permanent grazing buffet and barely affects the front-glass viewing experience.

If green water (free-floating algae) becomes a problem, scale back the photoperiod by an hour at a time rather than killing the algae you actually want.

## Diet & Feeding

The single biggest mistake new keepers make is treating reticulated hillstream loaches like a community algae eater that will accept any wafer dropped into the tank. They will eat wafers, but their primary nutrition comes from biofilm, and a tank without it will starve them slowly.

> **Biofilm grazer — needs a mature tank**
>
> These fish are not suited for new aquariums. Their natural food is aufwuchs — the slick coating of diatoms, microorganisms, and soft algae that takes weeks to develop on submerged surfaces. Cycle the tank fully, then run bright lighting for two to three weeks to build up brown diatoms before introducing your first loach.

### Grazing Behavior: Biofilm and Aufwuchs

Aufwuchs is the technical term for the layer of diatoms, green algae, microorganisms, and trapped detritus that builds up on submerged surfaces in any well-lit tank. To a reticulated hillstream loach, this is steak and potatoes. To most aquarists, it looks like the brown haze you scrape off the front glass.

The fastest way to keep a steady supply going is to grow it offsite. Set up a bucket or small tub of dechlorinated water with a handful of smooth river stones, place it in indirect sunlight, and let it sit for two to three weeks. The stones will turn green and brown as biofilm establishes. Rotate seasoned rocks into the loach tank and swap fresh ones in every few weeks. The persistent [brown algae phase](/guides/brown-algae-in-fish-tank) that frustrates most keepers is exactly what reticulated hillstream loaches were built to eat.

### Best Supplemental Foods: Repashy Soilent Green and Algae Wafers

Even with strong biofilm production, supplemental feeding fills out the diet. Repashy Soilent Green is the gold-standard prepared food for this species — a powdered algae-based gel mix that you cook into a firm jelly, then cut into squares and stick to the glass or a flat rock. Loaches will swarm a fresh patch within minutes.

High-quality sinking algae wafers (Hikari, Omega One) work as a backup. Drop one or two wafers two to three nights per week after lights out. Avoid bottom-feeder pellets formulated for catfish — those run too high in protein and too low in vegetable matter for hillstream digestion.

A small portion of frozen bloodworms or baby brine shrimp once a week supplies the trace protein that pure algae diets miss. Squirt the food directly onto rocks where the loaches graze — the strong flow will scatter loose food before they can find it.

### Why They Aren't Just "Scavengers"

Reticulated hillstream loaches are sometimes marketed as a "cleanup crew" addition that will live on whatever scraps the other fish miss. That framing kills loaches. They are specialized grazers with a specific diet, not opportunistic omnivores. A tank with no biofilm, no supplemental algae food, and no targeted feeding will starve them within a few months — even if other fish in the tank are thriving.

## Tank Mates & Compatibility

Reticulated hillstream loaches are peaceful with other species but require tank mates that share their cool, high-flow preferences. The wrong stocking combination forces you to compromise on the parameters that keep the loaches alive.

> **Peaceful and group-friendly**
>
> Keep three or more reticulated hillstream loaches together. They are social and mildly territorial — when kept singly or in pairs, the dominant fish concentrates fencing behavior on a single subordinate. Groups of three to five spread that pressure across the group and make the entire display calmer and more active.

### Conspecific Behavior: Why Groups of 3+ Work Best

Males engage in "fencing" or "topping" — a harmless wrestling behavior where two fish lock pectoral fins and push each other across a contested rock. This is normal social behavior, not aggression, and it ramps up in tanks with multiple males. Three loaches minimum, five to seven preferred. The fencing pressure spreads across the group rather than fixating on a single subordinate animal that gets bullied off every grazing surface.

You will also see "fluttering" — a quick wing-flap display loaches use to claim a rock from another approaching fish. It looks dramatic and rarely causes physical harm.

### Best Dither Fish: White Cloud Mountain Minnows and Danios

White Cloud Mountain minnows (*Tanichthys albonubes*) are the textbook reticulated hillstream loach companion. They share the same temperature range (60 to 72 degrees F is their sweet spot), tolerate strong flow, occupy the upper water column, and look like a flashing silver-and-red ribbon when kept in groups of 10 or more.

Pearl danios, zebra danios, and gold barbs (*Puntius semifasciatus*) work similarly — coolwater species that swim mid-column and ignore bottom-dwellers. Bristlenose plecos share the algae-eating niche without competing directly. Avoid any of the warmer-water species (tiger barbs, cherry barbs, most rainbowfish) — those need 78-plus and will overheat the loaches. For broader options, the [freshwater fish guide](/guides/freshwater-fish) covers coolwater-tolerant species you can mix in.

### Invertebrate Safety: Shrimp and Snail Compatibility

Adult hillstream loaches do not actively hunt cherry shrimp or other Neocaridina, and the two species coexist well in densely planted setups. Very small shrimplets (under 5 mm) may occasionally be eaten if they wander into a loach's grazing path — opportunistic, not predatory. Provide dense moss or hardscape gaps to give juvenile shrimp safe nursery space.

Amano shrimp (*Caridina multidentata*) are essentially loach-proof at adult size and add another biofilm-grazing animal to the cleanup crew. Nerite snails, mystery snails, and trumpet snails are all safe and add complementary grazing pressure on flat surfaces the loaches do not visit as often.

## Breeding Sewellia lineolata

*Sewellia lineolata* will spawn in the home aquarium without much intervention if conditions are right. Captive-bred stock from Vietnam and Eastern Europe now supplies most of the global market.

### Distinguishing Males vs. Females (Pectoral Fin "Shoulders")

Sexing requires close observation. Males develop noticeably broader, more muscular "shoulders" at the leading edge of the pectoral fins — picture a bodybuilder's deltoids. The first few pectoral rays also thicken and develop small tubercles in mature males.

Females are slimmer through the shoulders and noticeably rounder through the abdomen when carrying eggs. Looking down at a female from above shows a wider midsection compared to the streamlined male profile.

### Conditioning with Live Foods and High Flow

Spawning triggers in the wild are tied to wet-season runoff: cooler water, increased flow, and a flush of food washed in from the surrounding forest. Replicate this in the tank with a 30 to 40 percent water change using water 5 degrees F cooler than the tank, increased powerhead output, and a few days of heavy feeding with frozen bloodworms or baby brine shrimp.

Females ripe with eggs become visibly distended through the belly. Spawning typically happens at night against a flat vertical surface — the tank glass, a flat stone, or a piece of slate. Eggs are tiny (under 1 mm), translucent, and adhesive, and hatch in 7 to 10 days.

### Raising Fry in the Main Display

Reticulated hillstream loach fry are too small and too cryptic to spot easily, which is both a problem and a blessing. They typically hide in fine gravel, between cobbles, and inside filter intakes for the first month, feeding on microscopic biofilm that adult loaches cannot access. A mature, biofilm-rich tank can produce a small number of surviving fry every few months without the keeper noticing until juveniles appear at half an inch.

For higher survival rates, set up a dedicated grow-out tank with sponge filtration and seeded rocks from the parent tank. Fry accept powdered first foods like Hikari First Bites once free-swimming. Growth is slow — expect six months to reach an inch.

## Common Health Issues

Reticulated hillstream loaches are hardy when their environment is right but show two distinct failure modes that catch unprepared keepers off guard.

> **Cooler water than typical tropical**
>
> Do not house these loaches in a standard tropical community tank running at 78 to 80 degrees F. Warm water holds dramatically less dissolved oxygen, and reticulated hillstream loaches suffocate slowly even when other community fish appear fine. Their preferred range (68 to 75) is well below most tropical setups — plan their tank around them, not the other way around.

### Stress from Low Oxygen (Gasping at Surface)

The single most common symptom of trouble is a loach hanging at the water surface, mouth open, or pinned vertically against a return flow. This is acute oxygen stress and usually means the tank is too warm, the flow has dropped (powerhead failure, clogged intake), or stocking has outgrown the existing oxygen supply.

Immediate response: drop the temperature 2 to 3 degrees with a partial cool-water change, add an extra air stone or powerhead, and check that all filtration is running at full output. If the loach recovers within an hour, you found the problem in time. If gasping continues past 24 hours despite intervention, parasites or bacterial gill damage may be involved.

### Skin Flukes and Ich Treatment in Scale-less Fish

Hillstream loaches are scaleless, which means they absorb medications through the skin at higher rates than scaled species. Standard copper-based ich treatments at full dose are toxic and can kill within days.

If ich appears in a tank containing reticulated hillstream loaches, do not use a heat treatment — raising temperature to the levels required to kill ich (82–86 degrees F) will simultaneously suffocate the loaches, which cannot tolerate temperatures above 75–78 degrees F. The correct approach is to move affected fish to a separate quarantine tank and treat them there with a copper-free ich medication (Ich-X, ParaGuard) at the manufacturer's recommended dose, while leaving the loaches undisturbed in their cool, well-oxygenated main tank. The best option remains prevention: quarantine new fish in a separate tank for two weeks before introduction so the parasite never enters the main display.

For skin flukes (*Dactylogyrus*, *Gyrodactylus*), praziquantel at standard doses is safe and effective. Symptoms include flashing against rocks, rapid gill movement, and increased mucus production.

## Where to Buy & What to Look For

Sourcing healthy reticulated hillstream loaches matters more for this species than for almost any other freshwater fish. The supply chain from Vietnam to your local store can take weeks, and during that time the fish often have nothing to graze on.

### Identifying Healthy Specimens at Your LFS

Reticulated hillstream loaches spend most of their time stuck to the front glass, which gives you a perfect ventral view that you cannot get with most fish. Use it. A healthy loach belly is pale cream or off-white, smooth, and free of red marks, fuzzy patches, or visible internal lumps.

Look at the loach from above. A healthy specimen has a thick, slightly convex profile across the back and belly. An emaciated loach — what experienced keepers call "skinny disease" — appears flat or concave when viewed from above, with a visibly sunken belly and prominent dorsal ridge. The eyes also recede slightly into the skull as fat reserves disappear. A loach that has been emaciated for more than two weeks will rarely recover even with intensive feeding. Pass on any specimen showing the concave silhouette, no matter how cheap the price.

Also watch the gill plates. Rapid, labored breathing in a quiet store tank suggests gill damage or low-oxygen stress. Any loach hanging at the surface or pinned vertically against a return flow is in active respiratory distress and should not come home with you.

### Quarantining Wild-Caught vs. Tank-Bred Loaches

Tank-bred reticulated hillstream loaches from European or Vietnamese breeders arrive in better shape than wild-caught imports and are more likely to accept prepared foods immediately. Wild-caught fish are cheaper but carry higher parasite loads and longer feeding-recovery times.

Either way, quarantine for two weeks minimum in a separate tank with seeded biofilm rocks pulled from your display. Use praziquantel prophylactically for flukes during that window. Drip-acclimate slowly — 60 to 90 minutes — to match temperature, pH, and especially oxygen levels gradually. Never net a hillstream loach by the body; the suction cup belly resists detachment and the fins tear easily. Lift them by hand or with a soft container.

## Quick Reference

The summary below is what to screenshot and tape to the side of the tank.

- **Tank size:** 20 gallons long minimum (30-inch footprint preferred)
- **Temperature:** 68 to 75 degrees F (no heater needed in most homes)
- **pH:** 6.5 to 7.5; hardness 3 to 12 dGH
- **Flow:** 10 to 20x tank turnover via powerheads or river manifold
- **Substrate:** Smooth river stones over fine sand; avoid sharp gravel
- **Diet:** Aufwuchs (biofilm) primary; supplement with Repashy Soilent Green and quality algae wafers
- **Tankmates:** White Cloud Mountain minnows, gold barbs, danios, Amano shrimp, bristlenose plecos
- **Avoid:** Bettas, gouramis, angelfish, fancy guppies, anything needing 78°F+
- **Group size:** Three minimum; five to seven preferred
- **Difficulty:** Intermediate — easy parameters, demanding equipment
- **Lifespan:** 8 to 10 years in a properly oxygenated tank

**Find healthy reticulated hillstream loaches at a local fish store** — [Find stores near me](https://www.fishstores.org/near-me)

Reticulated hillstream loaches ship poorly and arrive emaciated more often than not. Inspecting the fish in person — watching it graze and checking the belly for sunken sides — is the only reliable way to bring home a healthy specimen.

## Frequently Asked Questions

### Do reticulated hillstream loaches need a heater?

Generally, no. They thrive in cooler water (68 to 75 degrees F). In most climate-controlled homes, the ambient temperature is sufficient. High temperatures are dangerous because warm water holds less oxygen, which is fatal for this species.

### Can they live with goldfish?

It is possible in large tanks, but not ideal. While temperature requirements overlap, goldfish produce high waste and may outcompete loaches for food. Furthermore, goldfish prefer calmer water, whereas loaches require high-velocity flow.

### What is the minimum tank size?

A 20-gallon long is the minimum for a small group. The footprint (surface area) is more important than height, as these fish spend their time on rocks, glass, and the substrate.

### Do they eat hair algae?

No. They primarily graze on biofilm and soft green algae (spot algae). They will not clear an infestation of black beard algae or hair algae; they require specialized grazing diets.

### Are they aggressive?

They are peaceful but territorial toward their own kind. You will see fluttering or topping where they chase each other off a choice rock, but they rarely cause physical harm.

---
*Source: [FishStores.org](https://www.fishstores.org/species/reticulated-hillstream-loach)*
*Last updated: April 24, 2026*