Assassin snail care guide

1How big do they get?

The identification key reports adults at about 20–35 mm, without naming a measurement axis. Aquarium Co-Op gives up to 25 mm shell length, while The Shrimp Farm gives about 13 mm. We use the identification key as a reference, not a guaranteed size for every trade animal. Do not compare its figure directly with a measured shell width.

Adult shell size

20–35 mm (Axis not stated) Reference adult size; the key does not state an axis. Aquarium size estimates differ. Fact source

2How long do they live?

A useful aquarium estimate is 2–3 years, as given by Splashy Fish. Treat it as a care-planning estimate: some individuals live longer, and feeding and water conditions affect survival.

Lifespan

2–3 years 04 years Typical aquarium estimate in retailer guidance; individual lifespan depends on care and may be longer. Fact source

3What do they eat?

They hunt other snails and scavenge animal material. Laboratory work found individual differences in prey choice. Maintain a feeding plan after the unwanted snails have gone; do not treat a predator as disposable aquarium equipment.

Diet type

Carnivore Predator and scavenger of animal food. Fact source

4Do they eat plants?

They are not kept as plant eaters. The cited husbandry account describes animal-based feeding. Damage to a plant should be investigated rather than attributed to an assassin simply because it was nearby.

Plant eating

No Not expected to graze plants: an inference from the described carnivorous feeding, not a guarantee against disturbance. Fact source

5Do they eat algae or clean the tank?

No: do not buy one to graze algae. Its feeding role is predatory and scavenging. It still produces waste and does not replace filter care or water changes.

Algae role

Low Not an algae-control animal. Fact source

6What eats them?

Avoid pufferfish and snail-eating loaches. An assassin’s ability to hunt other snails does not protect it from fish that eat snails.

Predators

Pufferfish and snail-eating loaches. Being a predator does not protect an assassin from fish that eat snails. Fact source

7Are they safe with shrimp, fish and other snails?

Do assassin snails eat shrimp?

Do not promise shrimp safety. An older expert account calls them harmless to shrimp, while the Fishkeeping.co.uk care sheet records occasional attacks. These reports do not quantify a reliable risk. Our precautionary advice is to keep them out of a shrimp breeding tank if losing shrimp would be unacceptable.

Other snails are an intended prey group. Do not assume a large mystery or nerite snail is guaranteed safe.

With shrimp

Caution Reports conflict; do not promise a shrimp-safe tank. Fact source

With fish

Caution Peaceful compatible fish only; snail-eating fish remain a risk. Fact source

With other snails

No Other ornamental snails can be prey. Fact source

8How many per tank?

For 1–2 assassins, use 20 litres or more as a starting recommendation, rounding The Shrimp Farm’s 5 US gallons (about 19 litres) upwards. Aquarium Co-Op suggests a smaller 2-US-gallon setup for one; our 20-litre recommendation gives a more conservative starting point. The aquarium needs an established filter, stable water and substrate they can enter. Other livestock and a population of prey snails may require a larger tank.

Starting tank volume with conditions

20 litres For 1–2 assassins in a mature, filtered tank with suitable substrate. A conservative starting recommendation, not a biological minimum; other livestock may need more space. Fact source

9Do they need a heater, or can they live in cold water?

The care-sheet recommendation is 22–27°C. Use a thermometer and a heater if needed to keep conditions stable. Experimental activity at lower or higher temperatures does not make those extremes suitable long-term care targets.

Recommended water temperature

22–27 °C 1530 °C Husbandry guidance for trade animals, not experimentally proven limits for every species. Fact source

10What water do they need?

The cited care sheet gives pH 6.8–8.0 and 10–25°dGH. Treat these as husbandry guidance for trade animals, not a validated requirement for every species in the complex. Check the needs of the rest of the aquarium too.

pH

6.8–8 pH 69 pH Care-sheet range; confirm suitability for the stock and other animals. Fact source

Hardness guidance with units

10–25 °dGH in the cited care sheet. Fact source

11How do they breed, and how fast?

Assassins have separate sexes and can reproduce in freshwater. Maidenhead Aquatics describes reproduction as slower than in common nuisance snails, with eggs laid singly. Plan food and space for offspring; slower breeding does not mean the population cannot grow.

Can reproduce in a freshwater aquarium

Yes Egg capsules develop into crawling juveniles. Fact source

Breeding speed

Not known Reported to reproduce more slowly than common nuisance snails; no fixed rate is supplied. Fact source

Pair needed

Yes Separate sexes; a group does not guarantee a particular sex ratio. Fact source

12What do the eggs look like, and how long do they take to hatch?

Look for a single egg inside a small, clear, roughly square capsule attached to a firm surface. Published care estimates differ: 3–4 weeks at Splashy Fish versus around two months at The Shrimp Farm. Expect the timing to vary with conditions rather than relying on a fixed hatch date. Juveniles often stay hidden in the substrate after hatching.

Reproduction type

Egg laying Fact source

Hatching time

Varies Splashy Fish reports about 3–4 weeks; The Shrimp Farm reports around two months. These differing care estimates do not establish one reliable hatch-day range. Fact source

13Are they good or bad, and how do I get rid of them?

A predator may reduce other snails, but it adds an animal that also needs care. Investigate excess food and the reason you want population control first. Never move assassins into a pond or waterway: their predation can threaten native snails.

Population growth concern

Not known Slower reproduction does not rule out an unwanted population. Plan food and homes for offspring. Fact source

14Are they nocturnal, and why do they hide?

They are usually described as nocturnal, and burrowing is normal. Food can bring them out of the substrate, so daytime activity is not automatically a problem. A snail missing from view may simply be buried.

Active time

Night Usually described as nocturnal; food can prompt emergence from the substrate, so this is not an exclusive timetable. Fact source

Burrows

Yes Provide accessible substrate; hidden animals may still be present. Fact source

15Can they survive out of water or climb out?

Use a secure lid as a precaution. We have not established a safe duration out of water for this group. Keep handling brief and do not use an air-exposure claim as a care target.

Secure lid needed

Yes A secure lid is our precautionary recommendation, not a measured escape frequency. Fact source

16Is it dead, or just not moving?

Consider burrowing and normal rest, but investigate unusual inactivity. Test water and temperature and seek experienced help if behaviour changes persist. An unmoving snail is not, by itself, a confirmed dead snail.

17Why is the shell damaged, and do they need calcium?

Yes, calcium is needed for shell growth. Check hardness and pH before adding supplements; needing calcium does not mean every aquarium needs a separate dose. Investigate deteriorating shells alongside water quality and feeding.

Calcium required

Yes Needed for shell growth. Test water hardness before deciding whether supplements are necessary. Fact source