Assassin snails Clea helena are freshwater carnivorous snails used in aquariums to control populations of other smaller snails like bladder, mts and ramshorn snails. They will also eat worms and any leftover fish food such as flakes or pellets. They are egg layers and are not hermaphrodites so you need both male and female for them to reproduce.

Make sure to provide an adequate tank size of at least 5 gallons for them to thrive although I have kept a single snail in 2 gallon tanks with no issues. Assassin snails are quite adaptable and can tolerate a wide range of water conditions. However, they prefer slightly alkaline water with a pH between 7.0 and 8.0 with a temperature of 20-28c.