OSAquatics · Think Before You Buy

Think Before You Buy

Not every fish offered for sale will thrive in the conditions most home aquaria can provide. This guide highlights species that are mis‑sold, wild‑caught, or ethically sensitive.

View species list Ethical aquatics framework

Brackish mis‑sold species

Fish sold as “community” species that actually need brackish water

These species are routinely sold as freshwater community fish, but naturally inhabit estuaries, mangroves, or tidal rivers and need brackish conditions long‑term.

Species	Why they shouldn’t be in typical freshwater tanks
Monos (Monodactylus spp.)	Brackish to marine schooling fish that grow large and need high salinity and long tanks; sold as “silver community fish” but fail long‑term in freshwater.
Scats (Scatophagus spp.)	Estuarine omnivores that grow big, produce heavy waste, and require brackish to marine conditions; not suitable for small freshwater community aquaria.
Colombian shark catfish (Ariopsis / Hexanematichthys spp.)	Often sold as “sharks” for freshwater tanks, but naturally migrate to brackish and marine waters and grow far too large for home aquaria.
Archerfish (Toxotes spp.)	Surface predators from mangroves and estuaries; need brackish water, large surface area, and specialised feeding—unsuitable for standard community tanks.
Wild‑type mollies	Many wild forms are coastal/brackish fish; long‑term health is poor in soft freshwater, yet they’re sold as generic community livebearers.
Halfbeaks (various genera)	Surface‑dwelling fish from coastal and brackish habitats; easily stressed, prone to injury, and often fail in small, busy freshwater community setups.

Next: “Algae eaters” & plecs

Wild‑caught “algae eaters” & plecs

Fish sold as tank cleaners that rarely thrive

Many of these species are wild‑caught, specialised grazers that starve, outgrow tanks, or suffer in bare, bright community aquaria.

Species	Why they shouldn’t be in typical freshwater tanks
Common plec (Hypostomus / Pterygoplichthys spp.)	Sold as small “algae eaters” but grow very large, produce heavy waste, and need big, well‑filtered tanks; often dumped when they outgrow community setups.
Royal pleco, blue‑eyed pleco, other L‑numbers	Wild‑caught, specialised wood‑eaters or grazers that need strong flow, high oxygen, and specific diets; not generic algae cleaners for small tanks.
Otocinclus spp.	Small wild‑caught grazers that rely on mature biofilm; often starve in new or sterile tanks and are very sensitive to transport and water quality.
Twig catfish (Farlowella, Sturisoma, etc.)	Delicate, specialised periphyton grazers that need stable, mature setups and are easily stressed; poor survival in typical community tanks.
Whiptail catfish (Rineloricaria, etc.)	Slender loricariids that need sand, cover, and stable conditions; often fail in bright, bare, high‑traffic community aquaria.

Next: Purchase with care

Purchase with care

Species with declining wild populations or fragile habitats

These species are not always critically endangered, but wild populations are declining, habitats are collapsing, or they are frequently wild‑caught. Ethical sourcing and choosing captive‑bred fish wherever possible is essential.

Species	Why they require careful, ethical purchasing
Melanotaenia boesemani Boesemani Rainbowfish	Wild habitat in Lake Ayamaru is collapsing; many imports are still wild‑caught. Captive‑bred lines vary in quality.
Melanotaenia praecox Neon Dwarf Rainbowfish	Habitat pressure from mining and agriculture; often sold as “tank‑bred” despite being wild‑caught.
Danio margaritatus Galaxy Rasbora	Wild stocks fragile; still collected in Myanmar. Captive‑bred fish are more ethical and hardier.
Tateurndina ocellicauda Peacock Gudgeon	Wild habitat in PNG is collapsing; most imports are wild‑caught. Captive‑bred fish are far more sustainable.
Poecilia wingei True Endler’s Livebearer	Wild populations nearly gone; most shop “Endlers” are hybrids. Ethical sourcing protects remaining pure lines.
Channa andrao Dwarf Snakehead	Wild‑caught pressure remains high; captive‑bred fish are more stable and ethical.
Corydoras panda Panda Cory	Wild populations vulnerable due to pollution and mining. Captive‑bred fish are widely available and preferred.
Chromobotia macracanthus Clown Loach	Wild populations declining due to over‑collection and habitat loss; most juveniles in the trade are wild‑caught. Slow maturation makes wild recovery difficult.
Trigonostigma heteromorpha Harlequin Rasbora	Still common in the hobby, but wild populations are shrinking due to peat swamp destruction and water pollution. Captive‑bred fish are the ethical choice.
Corydoras weitzmani Weitzman’s Cory	Endangered in the wild with a tiny native range; threatened by habitat degradation. Captive‑bred fish help reduce pressure on remaining wild stocks.

Next: Wild caught and unsuitable

Wild‑caught oddballs

Wild caught and unsuitable for typical community tanks

Many “oddball” species are highly specialised, almost always wild‑caught, and rarely thrive in standard community aquaria.

Species	Why they shouldn’t be in typical freshwater tanks
Glass catfish (Kryptopterus spp.)	Always wild‑caught. Transparent schooling fish needing large, calm groups and dim, planted tanks; easily stressed and prone to wasting in busy community setups.
Wild Corydoras spp.	Wild‑caught from cool, soft, shaded streams; suffer in small, warm, bright tanks with sharp substrates and inadequate group sizes.
Pencilfish (Nannostomus spp.)	Surface‑oriented blackwater fish needing calm, densely planted tanks; easily outcompeted and stressed in active community aquaria.
Splash tetras (Copella spp.)	Specialised surface spawners needing emergent surfaces and calm conditions; not suited to generic community tanks.
South American leaf fish (Monocirrhus polyacanthus)	Highly specialised ambush predator relying on live prey and dense cover; almost always wild‑caught and prone to starvation in community tanks.

Next: Common but threatened

Common but threatened

Popular aquarium species with declining wild populations

These species are widely sold in the aquarium trade, yet their wild populations are shrinking due to habitat loss, over‑collection, or environmental degradation. Choosing captive‑bred fish and supporting responsible sourcing helps reduce pressure on remaining wild stocks.

Species	Why they are threatened in the wild
Chromobotia macracanthus Clown Loach	Wild populations declining due to over‑collection for the aquarium trade and ongoing habitat loss in their native rivers.
Trigonostigma heteromorpha Harlequin Rasbora	Wild stocks shrinking as peat swamps disappear; pollution and habitat fragmentation continue to reduce natural populations.
Corydoras weitzmani Weitzman’s Cory	Endangered in the wild with a tiny native range; threatened by habitat degradation and restricted distribution.

Next: Think twice summary

Ethical aquatics

Not every fish offered for sale should be in your tank

Many of the species listed above are wild‑caught, from fragile habitats, or so specialised that they rarely thrive in typical home aquaria. Ethical aquatics means choosing species that can genuinely live well in the conditions we can provide, favouring captive‑bred stock and avoiding species whose wild populations are under pressure.