Minimum Tank Size: 29 Gallons (110 Liters)
Care Level: Moderately Difficult
Water Conditions: PH 6.5-7.5 and Moderately Hard to Very Hard
Temperature: 65-77 °F (18-25 °C)
Maximum Size: 3 inches (7.5 cm)
The assassin snail (Clea helena) is freshwater snail that is highly sought after in the aquarium trade for their ability to prey on pest snails. They are found throughout much of Southeast Asia, and are native to Thailand, Malaysia, and Indonesia.
They primarily inhabit small bodies of water, and are most commonly found in ponds or ditches. They prefer locations with a sandy or muddy substrates, and these conditions should be reproduced as closely as possible in the home aquarium.
Assassin snails do particularly well in captivity, and most will grow up to 3 inches (7.5 cm) in length. The average life span is around two years, though they can easily exceed this age in a well maintained aquarium.
Assassin snails really only thrive in mature aquariums, and the minimum tank size for this snail is 29 gallons (110 liters). At first glance, this may seem to be an overly large tank size for such a small snail, but it should be noted that they do not breathe air like most other aquarium snails. Because of this, they are very sensitive to the water quality.
They must be provided with a soft substrate that allows them to burrow. Sand is generally the best choice, but there are numerous other substrates on the market that will also work. Adult assassin snails spend much of their time in the substrate, and they often ambush other snails from their position of concealment there.
Assassin snails have no interest in aquatic plants, and are safe in any planted aquarium. In fact, many people keep these snails in aquascaped tanks to deal with any unwanted pest snails that may be accidentally introduced.
A word of caution though – there have been numerous reports of assassin snails eating fish eggs, and even immobile wrigglers. So they should not be kept in breeding tanks, unless you are breeding live bearers.
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An assassin snail’s natural diet is mainly composed of other species of snails and worms, though they are also opportunistic feeders. They will eat almost anything that they can scavenge, and this includes decomposing fish and other small invertebrates.
Because of their varied diet, they are very easy to feed in the home aquarium. If there is a significant snail population in their tank, then there is often no need to feed them at all.
However, if there are no snails for them to eat, then they should be fed with a high protein food. Some aquarists feed them frozen blood worms, or brine shrimp, but any sinking food will do. The best choices are either Wardley Shrimp Pellets , or Hikari Algae Wafers (just make sure they’re not spirulina), and usually you can just choose whatever food is most appropriate for the fish that share the aquarium with them.
Assassin snails have defined males and females, and are not hermaphroditic like many other snails. It is nearly impossible to sex these snails, so if you are planning to breed them, a minimum of six individuals should be introduced to ensure an adequate mix of the sexes.
When they begin to copulate, they will lock together for approximately 12 hours. After they are done, the female will then deposit several single eggs. The eggs are often deposited on plants or driftwood, though you may also see them on ornaments, or even the aquarium glass. They are roughly square in shape, with a brown sack at the center.
The eggs generally hatch after a few weeks (usually between 3-8 weeks), though the amount of minerals in the water can influence the incubation time. Once hatched, the juveniles will burrow into the substrate, and are rarely seen again until they reach maturity. Maturity is usually reached after about six months, and at this time, they will emerge from the substrate more regularly.
They breed very slowly for a snail, and so rarely become a pest on their own. However, they can be difficult to completely remove from an aquarium, since they spend so much of their time buried in the substrate.
Assassin snails themselves are preyed upon by larger cichlids, or any of the more common snail eating fish. While they are protected by an operculum, they will often become injured and stressed from the constant attacks of a fish. If the attacks continue, they will either die, or have a greatly shortened life span.
Almost any other snail that is kept with an assassin snail is at risk. While extremely large snails like apple snails are generally safe, it is not unknown for assassin snails to “gang up” on larger snails, and devour them. Only place these snails in an aquarium if you are prepared to lose any snails that share a tank with them.
Assassin snails are renowned for their ability to deal with problem snails in an aquarium, and just a handful of these snails can deal with even a massive Malaysian trumpet snail infestation. Because of this, they are rapidly growing in popularity, and more and more fish stores are starting to carry this snail.