Quick Stats
| Adult Size | 5–6 cm |
| Minimum Tank | 10 gal |
| Temperature | 20–27°C |
| pH Range | 7.0–8.0 |
| Hardness (GH) | 8–18 dGH |
| Difficulty | Easy |
| Temperament | Peaceful |
| Diet | Herbivore/Scavenger — algae, dead plant matter, blanched vegetables, fish food scraps |
| Schooling | 1–2 per 10 gal |
Tank Setup
Mystery snails (Pomacea bridgesii, sometimes sold as Pomacea diffusa) are large, attractive, and undemanding. A 10 gallon tank is enough for 1–2 snails; allow 5 gallons per additional snail. They need a tank with a lid — they explore above the waterline and can escape.
Water parameters: temperature 20–27°C, pH 7.0–8.0, hardness 8–18 dGH. The non-negotiable is calcium: harder water keeps their shells thick. In soft water, add cuttlebone or crushed coral. Without calcium, the shell erodes and the snail eventually dies.
Provide a small air gap (1–2 cm) between the waterline and the lid. Mystery snails breathe air using a siphon and need to surface regularly. They also lay their eggs above the waterline — without space, they'll hold the eggs and become egg-bound.
Tank Mates
Mystery snails are peaceful and ignored by most community fish. Their size and operculum (the 'door' they seal the shell with) protect them from casual predation. They are safe with shrimp, all peaceful community fish, and other snail species.
Compatible with: Tetras, Corydoras, Guppies, Bettas (usually), Cherry Shrimp, Amano Shrimp, Nerite Snails, and most tropical community fish. The exceptions are dedicated snail-eaters: Clown Loaches, Yoyo Loaches, Dwarf Puffers, and some cichlids.
Bettas sometimes nip at the snail's antennae, but this rarely causes real harm. If your betta is particularly aggressive, choose a different cleanup snail (Nerite). Otherwise, mystery snails and bettas coexist well.
Diet & Feeding
Mystery snails are primarily herbivorous. They eat algae, dead plant matter (not live plants — they're safe for planted tanks), blanched vegetables, and fish food scraps. They are one of the few apple snail species that will not destroy your plants.
Feed 2–3 times per week in addition to what they graze. Drop in an algae wafer, a slice of cucumber, or a piece of blanched spinach after lights-out. Remove uneaten vegetables after 24 hours to prevent water fouling.
Calcium supplementation matters. Without enough calcium in the water or diet, the shell thins and pits. Offer a piece of cuttlebone in the tank, or use a calcium block sold for snails and shrimp. Crushed coral in the filter also works.
Common Health Issues
The two main health issues are shell erosion (soft water — fix with calcium supplementation) and 'trapdoor' deaths (the snail seals itself in and dies, often from old age or poor water quality). A trapdoor that doesn't open after 3 days usually means the snail has died.
Copper is lethal — remove all snails before treating fish with copper-containing medications. Many standard fish medications contain copper; always check the label.
Lifespan is typically 1–2 years. They are not as long-lived as Nerite snails (3–5 years) but their larger size and brighter colours make them more visible in the tank. A mystery snail that reaches 6 cm is a mature adult.
Breeding
Mystery snails are not hermaphroditic — you need a male and a female to reproduce. Sexing is difficult; the easiest approach is to keep 3–4 snails and let them sort it out. They lay eggs above the waterline in a tan, calcareous cluster that looks like a small grape bunch.
If you don't want babies, simply remove the egg cluster and dispose of it (freeze for 24 hours first to ensure they're not viable). The cluster is obvious — you won't miss it. This is why mystery snails are called the 'good apple snail': they can't overrun your tank like pest snails because the eggs are visible and easy to remove.
If you do want to hatch them, leave the cluster above the waterline in humid air. Eggs hatch in 2–4 weeks depending on temperature. The tiny juveniles drop into the water and immediately start grazing. Provide plenty of algae and biofilm for the first few weeks.
Frequently Asked Questions
What size tank does a Mystery Snail need?
A minimum of 10 gallons for 1–2 snails, plus 5 gallons per additional snail. They need a tank with a lid — they explore above the waterline and can escape. Leave a 1–2 cm air gap below the lid for breathing and egg-laying.
Will Mystery Snails eat my plants?
No — Mystery Snails (Pomacea bridgesii) eat algae, dead plant matter, and fish food scraps. They are safe for planted tanks. This distinguishes them from the closely-related Apple Snail (Pomacea canaliculata), which is a serious plant-eater.
How can you tell male from female Mystery Snails?
Sexing is difficult visually. The only reliable method is to watch them mate, or to keep a group of 3–4 and let them sort it out. Females lay eggs above the waterline whether or not they're fertilised — so seeing eggs doesn't confirm a male is present.
How do Mystery Snails reproduce?
They are not hermaphroditic — you need a male and a female. Females lay tan egg clusters above the waterline. The eggs are easy to see and easy to remove if you don't want babies. This is why they can't overrun a tank the way pest snails do.