Pea clam (Sphaerium corneum) care guide

Group
Other invertebrates
Other names
Fingernail clam, European fingernail clam, Orb mussel, Horny orb mussel
Family
Sphaeriidae
Origin
Native to Europe and northern Asia (Palearctic), including Britain; introduced to North America
Water
freshwater
Maximum size
1.4 cm
Temperature
4–22°C
pH
7–8.5
Hardness
8–20 dGH
Minimum tank
20 litres
Care level
intermediate
Lifespan
1–3 years

Care

The horny orb mussel is a tiny freshwater clam up to about 1–1.4 cm with a rounded brown to grey shell marked with fine lines; young ones are yellowish. It is one of the 'pea' or 'fingernail' clams and lives in shallow, slow or still water in lakes, rivers and ditches, preferring rich water but avoiding heavy pollution. It can climb plants on its foot to find better feeding spots, and it can survive a long time without oxygen in cold water. UK native: The horny orb mussel is native to Britain. It needs a coldwater (unheated) tank or a pond, and should not be collected from the wild where that is not allowed, such as nature reserves or private waters without permission. Hitchhiker: it often arrives with pond plants. It is harmless and helps filter the water, but it is small and easily overlooked. It is rarely sold. Set-up: a coldwater tank or pond with a soft, muddy or sandy bottom and plants. The temperature and water figures here are general guidance rather than from a source. Feeding warning: filter feeders like this are hard to keep fed in aquariums and many slowly starve over weeks or months, even in good tanks. In a clean aquarium a pond with green water or a mature, planted tank is a better home. Copper: copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most other invertebrates. Never treat a tank holding them with copper, check the label of any fertiliser or medicine, and keep nets and buckets used for copper-treated tanks separate. Sources: Wikipedia (en.wikipedia.org/wiki/Sphaeriumcorneum). Checked October 2026.

Diet

Mainly a filter feeder on diatoms and other phytoplankton. When currents are low or food is short it feeds on deposits in the sediment. In tanks it needs green water, liquid fry foods or a mature pond.

Breeding

Pea clams are hermaphrodites that brood their young inside the gills and release tiny, fully formed clams, so one clam can start a population. They can breed readily in ponds.

Compatibility and tank mates

Harmless to fish, shrimp, snails and plants. Many fish, crayfish and loaches eat it.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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