Quick Stats
| Adult Size | 4–6 cm |
| Minimum Tank | 10 gal |
| Temperature | 15–25°C (unheated) |
| pH Range | 7.0–8.5 |
| Hardness (GH) | 8–25 dGH |
| Difficulty | Easy |
| Temperament | Peaceful |
| Diet | Detritivore/Herbivore — algae, biofilm, detritus, leftover food, blanched vegetables |
| Schooling | 1–2 per 10 gal |
Tank Setup
Japanese Trapdoor Snails (Bellamya chinensis, formerly Cipangopaludina chinensis) are large cold-water snails native to East Asia. They tolerate temperatures from 15–25°C, making them perfect for unheated tanks, outdoor tubs, and goldfish ponds. A 10 gallon tank comfortably houses 1–2 adults.
Water parameters: temperature 15–25°C (unheated), pH 7.0–8.5, hardness 8–25 dGH. The non-negotiable is calcium — harder water keeps their thick, dark olive shells intact. In soft water, supplement with cuttlebone or crushed coral. They slowly decline in acidic water.
No special substrate is needed — they live on the glass, plants, and hardscape. Provide plants (Java fern, Anubias, Vallisneria) for them to graze on. They breathe using gills (not a lung like pond snails), so they don't surface for air — but they do need well-oxygenated water. Standard filtration is fine.
Tank Mates
Japanese Trapdoor Snails are peaceful and ignored by most fish. Their size (up to 6 cm) and tough, dark shell make them difficult for fish to eat — even goldfish leave them alone. The operculum (the 'trapdoor' that gives them their name) seals the shell tightly when the snail retracts.
Compatible with: Fancy Goldfish (perfect cold-water overlap — the snails clean up leftover food), Weather Loaches, White Cloud Mountain Minnows, Rosy Barbs, American Flag Fish, Cherry Shrimp, Amano Shrimp, and all other snail species. They are the standard cleanup-crew snail for outdoor ponds.
Avoid housing with dedicated snail-eaters: Clown Loaches, Yoyo Loaches, Dwarf Puffers, and some cichlids. Even large goldfish may occasionally swallow small juvenile trapdoors — provide plant cover where juveniles can hide until they grow.
Diet & Feeding
Japanese Trapdoor Snails are detritivores and algae-grazers. They eat algae (soft green algae on glass and plants), biofilm, detritus, leftover fish food, dead plant matter, and blanched vegetables. They do not eat healthy live plants.
Feed 2–3 times per week in addition to what they graze. Drop in an algae wafer or a slice of blanched zucchini, cucumber, or spinach after lights-out. They are slower eaters than goldfish — feed them in the evening so they get food before fish pick it clean.
They are especially useful in goldfish tanks, where they clean up the copious leftovers that goldfish miss. A single trapdoor can keep a 30 gallon goldfish tank's substrate noticeably cleaner. They also graze on algae that goldfish ignore.
Common Health Issues
Japanese Trapdoor Snails are extremely hardy in cool water. The main health issue is shell erosion in soft or acidic water — fix with calcium supplementation (cuttlebone, crushed coral, or a calcium block). Their dark olive shells turn pitted and translucent when calcium is insufficient.
Copper is lethal — remove all snails before treating fish with copper-containing medications. Many standard fish medications contain copper; always check the label. They are also sensitive to rapid pH swings — acclimate new snails slowly over an hour.
Lifespan is typically 3–5 years. They grow relatively slowly for a snail — a 1 cm juvenile may take a year to reach 4 cm. They are larger and longer-lived than most aquarium snails, which makes them a 'premium' cleanup-crew choice.
Breeding
Japanese Trapdoor Snails are live-bearing — females give birth to fully-formed miniature adults (no egg stage). This is a major advantage over pest snails: they cannot overrun a tank because each female produces only 6–20 babies per year, not hundreds.
Sexing is difficult visually. The easiest approach is to keep 3–4 snails and let them sort it out. If you see a tiny perfect miniature of an adult on the glass, congratulations — you have a breeding pair. The juveniles are immediately self-sufficient and need no special care.
Population control is essentially never needed. Even a breeding group produces only a handful of juveniles per year. This makes Japanese Trapdoor Snails the safest cleanup-crew snail for keepers who don't want a snail explosion. The trade-off is that they reproduce slowly, so building a colony takes years rather than months.
Frequently Asked Questions
Are Japanese Trapdoor Snails pests?
No — they are live-bearing and reproduce very slowly, producing only 6–20 babies per year per female. They cannot overrun a tank the way pest snails (bladder snails, pond snails, ramshorns) can. They are the safest cleanup-crew snail for keepers who don't want a snail explosion.
Do Japanese Trapdoor Snails need a heater?
No — they are cold-water snails that prefer 15–25°C. An unheated tank in a normal house, an outdoor tub, or a goldfish pond is ideal. They tolerate brief freezes but should be brought indoors if water temperature drops below 5°C for sustained periods.
Can Japanese Trapdoor Snails live with goldfish?
Yes — they are the standard cleanup-crew snail for goldfish tanks and ponds. They tolerate the same cold-water temperatures, their tough shells protect them from goldfish predation, and they clean up the copious leftovers that goldfish miss. Provide plant cover for juvenile snails until they grow large enough to be safe.
How big do Japanese Trapdoor Snails get?
Up to 6 cm in shell height — among the largest commonly-available aquarium snails, second only to Apple Snails. They grow slowly: a 1 cm juvenile may take a year to reach 4 cm. They are long-lived for snails, typically 3–5 years.