Freshwater invertebrates
Shrimp, snails, crayfish and crabs have constraints fish keeping never has to consider — copper sensitivity, calcium for moulting and shell growth, and a hardness floor below which moults fail.
Shrimp (25)
- Amano shrimpThe most effective algae-eating invertebrate available, and larger and longer-lived than a cherry shrimp.5 cm
- Bamboo shrimpA large filter-feeding shrimp that fans the current with modified feeding limbs rather than picking at surfaces.10 cm
- Blue leg Poso shrimpA pale body on bright blue legs, from a single lake on a single island.2.5 cm
- Blue pearl shrimpA pale blue Neocaridina from southern China, kept in the same way as the cherry shrimp and distinguished from it by species rather than by colour line.3 cm
- Bumblebee shrimpBlack and cream banding on a small stocky shrimp, and a species regularly confused with the crystal reds it is sold beside.2.5 cm
- Cardinal Sulawesi shrimpThe dwarf shrimp that inverts every rule the others taught: it needs warm, hard, alkaline water, and the soft acidic conditions that suit Caridina and Neocaridina everywhere else will kill it.2 cm
- Cherry shrimpThe most forgiving dwarf shrimp in the hobby and the usual first one.4 cm
- Crystal red shrimpA selectively bred line of the bee shrimp, needing soft, acidic, low-mineral water held within a narrow band.3 cm
- Ghost shrimpSold cheaply as live food and as an algae eater, and it is neither reliably.5 cm
- Giant river prawnThe largest freshwater prawn in the aquarium trade and one of the most widely farmed animals in the world.32 cminvasive risk
- Green babaulti shrimpAn Indian Caridina that keeps like a Neocaridina — tolerant of a wide hardness range, breeding in fresh water without a larval stage — and does not hybridise with the crystal and tiger shrimp it is often kept beside.3 cm
- Malawa shrimpThe Sulawesi shrimp that does not need Sulawesi water.2 cm
- Ninja shrimpNamed for changing colour — brown, green, red or striped, sometimes within a day.3 cm
- Opae ulaA small red shrimp from Hawaiian coastal pools that lives in brackish water, feeds on the algal film growing on rock, and survives for decades in closed systems with almost no maintenance.1.5 cm
- Red line Sulawesi shrimpA white lengthwise stripe over red, with a yellow patch behind the eye.2.5 cm
- Red nose shrimpA slender, near-transparent shrimp with a long red rostrum, which it holds pointed forward as it hovers in midwater — unusually for a dwarf shrimp it swims rather than grazes the bottom.4 cm
- Simon's shrimpA small translucent Caridina from Sri Lanka that breeds in fresh water without a larval stage, which puts it in the small group of Caridina a keeper can actually establish a colony of.2.5 cm
- Singapore flower shrimpThe bamboo shrimp's wider-ranging relative, distinguished by a row of spines along the rostrum that the commoner species lacks.9 cm
- Snowball shrimpNamed for its eggs rather than its body: the female carries clutches of opaque white eggs that look like a cluster of snowballs under her tail.3 cm
- Sulawesi harlequin shrimpA boldly banded Sulawesi shrimp restricted to one lake, and one of the few dwarf shrimp with a genuinely striking pattern rather than a colour.2.5 cm
- Sulawesi sponge shrimpA shrimp that lives on a freshwater sponge, which is an association almost nothing else in the hobby has.1.5 cm
- Sunkist shrimpA filter-feeder from the upper reaches of short island streams, which it reaches by climbing wet rock around waterfalls as a juvenile.6 cm
- Tiger shrimpA striped Caridina that is markedly more tolerant of ordinary water than the crystal red shrimp it is usually kept beside, and which will hybridise with it.3 cm
- Vampire shrimpA heavy-bodied filter-feeding shrimp that reaches 15 cm and fans the current with four modified feeding limbs.15 cm
- Whisker shrimpSold as a ghost shrimp and routinely bought as one, and it is a different animal: it carries long chelipeds, it hunts, and it will take a sleeping fish.7 cm
Snail (26)
- Assassin snailA predatory snail that hunts other snails, burrowing through sand to find them.2.5 cm
- Big-ear radixA pond snail with a broad flared aperture, arriving in aquaria on plants and generally treated as a pest.3 cm
- Black devil snailA long black spire, often eight centimetres of it, on a snail that grazes hard surfaces without touching plants.8 cm
- Black neriteThe largest nerite in general trade and the fastest — a plain dark shell over a body that moves visibly quickly across glass.3.5 cm
- Bladder snailThe snail nobody buys and almost everybody ends up with, arriving on plants as eggs.1.5 cminvasive risk
- Channelled apple snailOne of the most damaging aquatic invasive species in the world, responsible for major rice crop losses across South-East Asia, and a snail that will strip a planted aquarium.8 cm
- European river snailA temperate livebearing snail that filter-feeds as well as grazing, drawing suspended particles across its gill — a habit almost no other aquarium snail has, and one that makes it useful in a pond and largely invisible in a tank.4 cm
- Giant ramshorn snailSold as a ramshorn and actually an apple snail, which is the whole point: it will strip a planted tank exactly the way a Pomacea does, and it has been deployed deliberately as a biological control for weeds and for schistosomiasis-carrying snails.6 cminvasive risk
- Great pond snailA large temperate pond snail with a pointed shell and a genuine appetite for aquarium plants, which separates it from the ramshorns and bladder snails it arrives alongside.6 cm
- Great ramshorn snailThe largest ramshorn in the hobby at around 3 cm across, and one of the few aquarium snails with haemoglobin — its blood is red, which is what lets it work in water too poorly oxygenated for most invertebrates.3.5 cm
- Hercules snailA large heavy-shelled Sulawesi stream snail reaching seven centimetres, grazing biofilm from rock in strong current.7 cm
- Horned nerite snailA small nerite carrying blunt shell spines, sold as a more decorative version of the ordinary nerite and behaving in exactly the same way — an efficient algae grazer whose eggs will not hatch in fresh water but are laid all over the tank anyway.2 cm
- Island apple snailA very large apple snail that eats aquatic vegetation at a rate that has removed it from entire wetlands, and which is among the most damaging introduced freshwater molluscs anywhere.15 cm
- Japanese trapdoor snailA livebearing coldwater snail with an operculum it seals itself behind, kept mostly in ponds and mostly for the same reason as in aquaria: it eats detritus and does not eat plants.6 cminvasive risk
- Limpet neriteA nerite that has abandoned the spiral: the shell is a flattened cap clamped to rock, which lets it hold station in current that would roll an ordinary snail away.3 cm
- Malaysian trumpet snailA burrowing, livebearing snail that turns over the substrate and prevents anaerobic pockets forming in deep sand.3 cminvasive risk
- Marten's viviparous snailA South-East Asian livebearing snail that filters suspended particles from the water as well as grazing surfaces, which makes it one of the few aquarium snails that genuinely helps with cloudy water.4.5 cm
- Mystery snailA large, peaceful, plant-safe apple snail that breathes air through a siphon and lays pink egg clutches above the waterline.6 cm
- Nerite snailThe most effective algae-eating snail available, and one that cannot overpopulate a freshwater tank because its larvae need salt water.3 cm
- Pagoda snailEach whorl carries a ring of blunt spines, so the shell reads as a stack of tiered roofs.5 cm
- Quilted melaniaA burrowing thiarid that reproduces parthenogenetically, arrives on plants, and has become one of the more successful freshwater invaders in the Americas.3 cminvasive risk
- Rabbit snailA large livebearing snail with a wrinkled face and a slow deliberate gait, which produces one fully formed offspring at a time rather than a clutch.10 cm
- Ramshorn snailA flat-coiled snail that arrives uninvited on plants more often than it is bought.2.5 cm
- Spixi snailThe apple snail that mostly leaves plants alone, striped dark on cream and considerably smaller than the mystery snail.3.5 cm
- Towuti rabbit snailA rabbit snail that can actually be named: endemic to Lake Towuti, and the species behind a good part of the trade's yellow-bodied stock.8 cm
- Zebra nerite snailThe striped nerite most people picture when they hear the name, with a golden shell banded in black.2.5 cm
Crayfish (18)
- Blue moon crayfishDescribed formally in 2015 from animals already circulating in the aquarium trade, with a marbled blue and cream carapace that gives it its name.12 cm
- Cajun dwarf crayfishA 3 cm crayfish small enough to be a genuine community animal and interesting enough to carry a tank on its own.4 cm
- Common yabbyAn Australian crayfish that survives drought by sealing itself into a burrow for months, which is also why its specific name is destructor — it undermines dam walls and irrigation banks.30 cminvasive risk
- Dwarf Mexican crayfishA 4 cm crayfish, small enough not to threaten most fish and interesting enough to carry a tank on its own.5 cm
- Electric blue crayfishThe bright blue crayfish sold as a centrepiece for a community tank, which it cannot be: it takes fish, shrimp, snails and plants, and it does so at night.13 cminvasive risk
- Least dwarf crayfishThe smallest crayfish in the hobby at around 2 cm, which is small enough to share a tank with dwarf shrimp without ending the colony.2.5 cm
- Marbled crayfishEvery individual is a genetic clone of its parent, and a single animal can found a population.13 cm
- Montezuma dwarf crayfishA high-altitude dwarf crayfish from the lakes around Mexico City, larger than the orange CPO and from noticeably cooler water.6 cm
- Noble crayfishEurope's largest native crayfish and, until the twentieth century, its most abundant.18 cm
- Orange tip crayfishA blue-green New Guinea crayfish with bright orange claw tips, described only in 2015 from material already circulating in the aquarium trade.11 cm
- Papua blue crayfishA New Guinea Cherax in strong blue and orange, smaller than the Australian species and sold heavily on colour.13 cm
- Red swamp crayfishOne of the most damaging freshwater invasive species in the world, farmed for food, sold as an aquarium animal, and named individually on the EU list of invasive alien species of Union concern.15 cm
- Redclaw crayfishA large tropical crayfish farmed for food across the tropics and sold to aquarists on the strength of the blue colour form.25 cminvasive risk
- Rusty crayfishA North American crayfish spread far beyond its native basin largely through use as fishing bait, where it displaces native crayfish and strips aquatic vegetation.13 cm
- Signal crayfishA North American crayfish introduced to Europe for aquaculture in the 1960s, which carries the crayfish plague without dying of it and has driven native European crayfish towards extinction across much of the continent.18 cm
- Slough crayfishThe sexually reproducing species from which the all-female marbled crayfish arose in the aquarium trade.11 cm
- Spiny-cheek crayfishOne of the oldest crayfish introductions in Europe and a carrier of the crayfish plague that has removed native European crayfish from whole catchments.12 cm
- Zebra crayfishA boldly striped New Guinea crayfish with long slender claws, reaching around twelve centimetres and among the more manageable Cherax in the trade.13 cm
Crab (9)
- European freshwater crabA temperate European crab that lives partly out of water and hibernates through the winter — the only crab in this catalogue that expects a cold season.6 cm
- Orange-arm vampire crabA semi-terrestrial crab whose females carry their young on the back of the carapace after hatching — a behaviour that gives the species its name and is rare among crabs.3 cm
- Panther crabOne of the few genuinely and fully aquatic freshwater crabs in the trade — it does not need land, which separates it from almost everything else sold as a freshwater crab.7 cm
- Red apple crabA deep red-orange crab about the size of a walnut that spends nearly all its time out of water.4 cm
- Red claw crabThe crab most often sold to freshwater keepers, and a brackish mangrove animal.5 cm
- Red devil vampire crabA semi-terrestrial crab with orange-red claws and pale eyes, described in 2015 from animals already in the aquarium trade.2.5 cm
- Thai micro crabA crab with a body about the size of a lentil that lives in floating plant roots and filters particles out of the water with hairy claws.1 cm
- Tioman vampire crabA small orange-and-brown land crab from Tioman Island that lives beside water rather than in it, needing a humid terrestrial area with a shallow pool.3 cm
- Vampire crabA small, brightly coloured crab that is not an aquarium animal at all: it needs land, humidity and only a shallow water area.2.5 cm
Other invertebrate (6)
- Asian clamThe only bivalve in this catalogue, and one of the most costly freshwater invaders in the world — it blocks industrial water intakes at a scale measured in millions.4 cm
- Chinese pond musselA pond mussel that reached thirty centimetres and most of Europe in about fifty years, carried as larvae on the gills of stocked carp.30 cminvasive risk
- Duck musselSmaller and thicker-shelled than the swan mussel, and the one more likely to be found in a river than a pond.12 cm
- Painter's musselNamed because its shells were once used to hold artists' pigment.10 cm
- Swan musselEurope's largest freshwater mussel, sometimes twenty centimetres of it, buried to the hinge in silt with only the siphons showing.20 cm
- Zebra musselA small striped mussel that attaches to hard surfaces with byssal threads and forms dense encrusting beds, blocking water pipes and smothering native mussels.4 cm