This reviewed buying guide covers 10 freshwater fish. A photograph appears only when the image shows the exact species alive in an aquarium or other suitable submerged setting and its reuse record is complete; the reviewed profile remains available without substitute imagery while a qualifying photo is sourced.
Use the guide at the retailer to compare breathing, posture, body condition, skin, fins, eyes, and behavior with what is normal for the species. Look at the whole sales system, ask about feeding and recent arrivals, and quarantine every new fish before it shares water or equipment with an established aquarium.
This is an observation guide, not a diagnosis. A fish that looks healthy can still carry pathogens, while transport, lighting, age, sex, and social position can change normal appearance and behavior.
Content transparency
AI-generated draft, human-reviewed publication
This guide was drafted with generative AI used to organize research and prepare an initial version. The AI output was not treated as an authority or source. Dan from the Simply Submerged Aquatics team reviewed the published guide for accuracy and completeness within the scope recorded below.
What the human review covered
- Species identities, scientific names, and public fish-selection copy
- Healthy signs, purchase warning signs, and diagnostic limitations
- Species-normal behavior and temperament distinctions
- Source records, image licences, and TankWise app statements
Key takeaways
- Watch the complete sales tank before choosing an individual fish.
- Compare breathing, posture, body condition, skin, eyes, fins, and response rather than relying on one sign.
- Allow for normal species behavior, including resting, hiding, schooling, feeding patterns, territorial display, and social position.
- Confirm the scientific identity and eventual aquarium needs before buying.
- Only approved exact-species aquarium photographs are shown; a reviewed profile remains available without an image when photography is pending.
- A healthy-looking fish still needs a suitable aquarium; compare it with your saved tank in TankWise before buying.
Store-side field guide
10 fish at a glance
Match the store label to the fish, then jump straight to its healthy and warning signs.
GuppyPoecilia reticulata
Black Skirt TetraGymnocorymbus ternetzi
Pygmy CorydorasCorydoras pygmaeusCommon OtocinclusOtocinclus vittatusRoseline Shark or Denison BarbSahyadria denisonii
Ranchu GoldfishCarassius auratus
Jack Dempsey CichlidRocio octofasciata
Cobalt Blue Zebra CichlidMaylandia callainos
Bumblebee CatfishMicroglanis iheringi
Exclamation-point RasboraBoraras urophthalmoidesCheck the sales tank before the fish
Watch before anyone taps the glass, feeds the fish, or reaches for a net. Compare breathing, posture, body condition, skin, fins, eyes, and behavior across the group rather than choosing only by color or activity.
Pause if a tankmate is dead, unable to balance, extremely thin, ulcerated, heavily spotted, covered in growth, or breathing with pronounced effort. Ask when the fish arrived, whether it has eaten, and whether nearby tanks share filtration.
A feeding response is useful evidence, but it does not prove that a fish is disease-free. Quarantine every new arrival separately and avoid sharing wet equipment with the established aquarium.
- Observe the group from a distance before selecting a candidate.
- Compare the candidate with several fish of the same species when possible.
- Confirm the store label and scientific identity.
- Ask about arrival date, feeding, treatment history, and shared filtration.
- Check the species against your aquarium in TankWise before purchase.
Guppy
Poecilia reticulata
What to notice
Review these species-specific points together: Clamped or frayed fins, wasting, bent spine, shimmying.
Confirm that sex, pregnancy, courtship, persistent harassment, body condition, and shimmying are interpreted carefully.
Black Skirt Tetra
Gymnocorymbus ternetzi
What to notice
Review these species-specific points together: Body depth, fin damage, white spots, excessive nipping.
Confirm that schooling, chasing, colour change, and social position are explained without treating every shy or subordinate fish as ill.
Pygmy Corydoras
Corydoras pygmaeus
What to notice
Review these species-specific points together: Full belly, barbels, clear skin, midwater group activity.
Confirm that resting, hiding, bottom-feeding, nocturnal activity, barbel condition, and breathing behaviour are described in a species-appropriate way.
Common Otocinclus
Otocinclus vittatus
Review these species-specific points together: Rounded belly, intact mouth, clean gills, evidence the fish is eating.
Confirm that resting, hiding, bottom-feeding, nocturnal activity, barbel condition, and breathing behaviour are described in a species-appropriate way.
Roseline Shark or Denison Barb
Sahyadria denisonii
Review these species-specific points together: Mouth or scale damage, strong swimming, schooling, adult tank length.
Confirm that schooling, chasing, colour change, and social position are explained without treating every shy or subordinate fish as ill.
Ranchu Goldfish
Carassius auratus
What to notice
Review these species-specific points together: Spine and tail-set shape, balanced swimming, body symmetry, raised scales.
Confirm that variety-specific body shape is not confused with deformity and that swimming balance, scale position, fins, eyes, and specialised features are checked.
Jack Dempsey Cichlid
Rocio octofasciata
What to notice
Review these species-specific points together: Head pits, fin and jaw damage, clear eyes, territorial aggression.
Confirm that territorial display, pair or group dynamics, mouthbrooding where relevant, and persistent bullying are clearly separated.
Cobalt Blue Zebra Cichlid
Maylandia callainos
What to notice
Review these species-specific points together: Body weight, mouth injury, torn fins, territorial pressure.
Confirm that territorial display, pair or group dynamics, mouthbrooding where relevant, and persistent bullying are clearly separated.
Bumblebee Catfish
Microglanis iheringi
What to notice
Review these species-specific points together: Full belly, intact barbels, clear skin, nocturnal feeding response.
Confirm that resting, hiding, bottom-feeding, nocturnal activity, barbel condition, and breathing behaviour are described in a species-appropriate way.
Exclamation-point Rasbora
Boraras urophthalmoides
What to notice
Review these species-specific points together: Correct identity, body weight, color, group confidence.
Confirm that schooling, chasing, colour change, and social position are explained without treating every shy or subordinate fish as ill.
Sources and further reading
These references provide scientific or technical background and disclose how TankWise works. External references do not imply that every current TankWise catalog value was sourced from, or reviewed by, those organizations. See the checker methodology and known limits for that distinction.
- Selection of FishMerck Veterinary Manual
Veterinary-reviewed guidance on assessing a fish, its environment, skin, fins, eyes, movement, and alertness before purchase.
- Selecting a FishAmerican Veterinary Medical Association
Supports checking adult needs, body condition, breathing, behavior, and the wider sales system, while recognizing that a normal-looking fish may still carry disease.
- Pet Fish HealthRSPCA
Species-aware health context for appetite, breathing, alertness, eyes, fins, scales, and swimming.
- FishBase Species SearchFishBase
Scientific identity, distribution, biology, size, and cited species information used alongside other qualified sources.
- TankWise checker methodology and known limitsSimply Submerged Aquatics
The inputs, rules, safety limits, and uncertainty boundaries behind the TankWise aquarium comparison.
- Guppy species recordFishBase
Species reference for Guppy (Poecilia reticulata).
- Black Skirt Tetra species recordFishBase
Species reference for Black Skirt Tetra (Gymnocorymbus ternetzi).
- Pygmy Corydoras species recordFishBase
Species reference for Pygmy Corydoras (Corydoras pygmaeus).
- Common Otocinclus species recordFishBase
Species reference for Common Otocinclus (Otocinclus vittatus).
- Roseline Shark or Denison Barb species recordFishBase
Species reference for Roseline Shark or Denison Barb (Sahyadria denisonii).
- Ranchu Goldfish species recordFishBase
Species reference for Ranchu Goldfish (Carassius auratus).
- Jack Dempsey Cichlid species recordFishBase
Species reference for Jack Dempsey Cichlid (Rocio octofasciata).
- Cobalt Blue Zebra Cichlid species recordFishBase
Species reference for Cobalt Blue Zebra Cichlid (Maylandia callainos).
- Bumblebee Catfish species recordFishBase
Species reference for Bumblebee Catfish (Microglanis iheringi).
- Exclamation-point Rasbora species recordFishBase
Species reference for Exclamation-point Rasbora (Boraras urophthalmoides).
Frequently asked questions
Can a fish that looks healthy still carry disease?
Yes. Visual screening can identify reasons to pause, but it cannot prove that a fish is free of pathogens or parasites. Quarantine new arrivals and avoid sharing wet equipment with an established aquarium.
Should I buy from a tank containing a dead or visibly distressed fish?
Pause and ask what happened, whether the tanks share filtration, and what action the retailer is taking. Choosing another fish from the same water does not remove shared exposure.
Is unusual color, hiding, or resting always a sign of illness?
No. Lighting, transport, age, sex, social position, and species-normal behavior can change appearance and activity. Review breathing, posture, body condition, skin, fins, eyes, and the condition of the whole tank together.
Why does this guide include 10 fish rather than ten?
Only fish with a licensed live or submerged exact-species reference photograph were included. Fish awaiting suitable photography remain unpublished instead of being represented by stock or substitute species.
Where does TankWise fit?
This guide helps screen the individual fish. TankWise then compares the species' needs with your aquarium, water, and current livestock. It does not diagnose illness or guarantee compatibility.