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Caresheet: Assassin snail | Clea helena

Last Updated January 23, 2020
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Even the most careful aquarist can end up with a snail infestation, which can be rather frustrating! In the search for a solution they often look up which fish eat snails and eventually end up with a puffer or clown loach, which is entirely unsuitable for their setup and an even bigger problem than before. Luckily, there is another option: assassin snails, so called because they skillfully hunt down and cannibalize other snails.

Keep reading for more information on keeping assassin snails and their effectiveness when dealing with a snail infestation!

Minimum tank size5 gal (19 L)
Temperature75-80 °F/24-26.5 °C


Assassin snail, Clea helena (sometimes Anatome helena), bumblebee snail

Assassin snail natural habitat

Assassin snails are naturally found in Southeast Asia, where they reside in all types of streams and ponds with sand substrate.

Assassin snail appearance

Their conical, yellow and dark brown striped shell makes assassin snails an attractive addition to any aquarium, not just the ones with a pest snail infestation! They usually grow to a maximum size of around 0,5 inch/1,3 cm, although slightly bigger snails have been reported.

Like many other snail species these use a siphon, which can usually be seen sticking out of the shell, to breathe. Telling males and females apart is not really possible.

Struggling with a snail infestation in your aquarium? Strangely, the solution is... a snail. Find out everything you need to know about keeping assassin snails! #aquariums
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Assassin snail requirements

Although they are not really group animals, keeping at least 3-4 assassin snails is usually recommended. There seems to be a bit confusion about the minimum tank size for them, but at least 10 gallons (38L) should definitely be enough for a group that size!

Because assassin snails naturally bury themselves and wait for their prey to appear a sand substrate is preferred, although it’s not a must. The water should ideally not be too soft, as this could lead to deterioration of the shell, and as with all tropical fish and invertebrates the aquarium should be filtered, heated, fully cycled and free of ammonia and nitrites.

Assassin snail tankmates

If you’re thinking about introducing assassin snails into your aquarium, keep in mind that they don’t just eat pest snails. Although not all sources agree on whether they will also devour ornamental nerite snails and even large mystery snails, you should definitely assume they will and avoid keeping them together. In fact, assassin snails will eat about anything that comes their way: planaria, fish eggs, and according to some aquarists, even the occasional dwarf shrimp fry.

This means that if you’re breeding your fish or shrimp and want to avoid any risks, you may want to skip the assassin snails. Any larger tankmates that require the same water values are fine, as long as they’re not snail eaters!

Assassin snail diet

As mentioned before, assassin snails are not strictly snail eaters. While they can wipe out entire populations of pond snails, ramshorn snails and Malaysian trumpet snails, they are opportunists that will eat anything that comes their way. This means live prey, deceased tankmates, commercial fish foods, frozen foods and even algae.

To feed a steady supply of snails once the initial population is gone, you can ask your local aquarium store or breed snails in a small separate tank as described here. However, there is no need to worry if you do ever (temporarily) run out. Feeding your assassins other protein rich foods such as bloodworms is fine as well!

Assassin snail behavior

Although they will quickly flock to any food that is offered, assassin snail behavior is very different from that of most of their herbivorous cousins. They don’t move around foraging, but the hunting process is quite interesting to watch!

When they’re hunting for live snails, they will bury themselves into the substrate whenever possible and wait there with just their proboscis (feeding tube) sticking out until an unsuspecting victim gets close enough to assassinate. If there is no sand substrate available to bury in, they will often actively move around the aquarium while searching for other snails to devour.

Assassin Snail - Clea Helena

Breeding assassin snails

Fortunately, while breeding assassin snails is not very difficult, it’s not as easy as breeding pest snails or you would soon end up with an assassin snail infestation. If you do end up with more assassins than you can house after a while, it’s usually not too difficult to find another aquarist or aquarium store willing to take a few.

Like mystery snails and unlike pest snails, assassin snails are not hermaphrodites where both sexes can reproduce. Instead, only the female can reproduce, which means a lot less offspring. To breed, get a big enough group to have a good chance of having both sexes in there, as the males and females can’t be told apart.

As long as there are plenty of snails or other nutrient and protein rich foods available, the snails will take it from there. You should soon see light colored, square shaped egg sacs appear. After hiding for a while until they’re big enough, the baby snails will join the adults during feeding time.

Buying assassin snails

When buying, look for assassin snails that are actively moving around, eating or stalking prey in the substrate. If the operculum is closed, there may be something wrong with the snails. A flaky looking or deteriorating shell is a sign of calcium deficiency, which may be too late to reverse. If you’re ordering online, be sure to look for a trustworthy seller with plenty of good reviews like InvertObsession!

When introducing your snails into their new home, make sure you acclimate them properly so they can slowly adapt to the different water values. Skipping this step means a lot of stress for the snails, which can unfortunately sometimes be fatal!


Although assassin snails do a great job at keeping aquariums snail free, their striking stripes and interesting feeding behavior also make them a great addition to setups without a snail problem. They are fun to watch when hunting and do well in a wide range of water conditions!

If you have any more questions about keeping assassin snails or want to share your experiences with them, be sure to leave a comment below. Happy snail keeping!

Cover photo: Om Nom Nom by f_jean

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  • Reply Ynot February 8, 2019 at 3:55 am

    How often do / should Assasins eat? I’ve been acclimating and studying 5 of them in an isolated in-aquarium specimen box: aerated, water changed daily, with 3 Pond Snails per Assasin who are fed blanched lettuce. It has been a week and no signs of empty shells. If anything, I’ve seen several times where the pond snails crawl completely over top of the assassins, or congregate as a group on top of one of the Assasin’s shells for a while. A couple of times a pond snail has gone nose to nose with us our son, only to have the assassin pull it’s proboscis back, and either retreat, or steer around the pond snail. Today, just to see if something else would happen, I placed a Cichlid food pallet in the isolation tank (it contains a high quantity of salmon and shrimp). The pond snails loved it and immediately surrounded it. The other assassins have ignored it, with one cruising past it but paying no mind. Is it normal for Assassins to wait so long between eating, or do I have the only group of vegetarian assassins in the Midwest?

    • Reply Mari February 8, 2019 at 6:16 pm


      Oh dear, vegan assassin snails! In all seriousness, I’ve never studied this to the degree that you’re doing now and as such I haven’t a clue how long they go without eating while they’re acclimating. Honestly I’d just leave things be and not worry too much; as long as your water quality is good and you’re following all of the assassins’ care guidelines then it should all turn out fine. Maybe they’ll start eating in the specimen box, maybe they’ll wait until they’re released into the main tank.

      Good luck, I hope it all goes well!

  • Reply Emily H. November 5, 2018 at 1:11 am

    Are these great for baby betta?

    • Reply Mari November 5, 2018 at 1:32 pm

      In what sense? They can be kept with Bettas usually, yes, but they wouldn’t have any specific advantages for your fish.

  • Reply Paulo Lisboa March 16, 2018 at 7:13 pm

    I’ve got a pair of big Neritina Pulligera. Will they be in risk if I join a pair of assassin killers?

    • Reply Mari March 17, 2018 at 11:47 am

      There’s no way to be sure whether they’ll be eaten of not, but I personally wouldn’t take the risk with such beautiful snails!

  • Reply Gaby October 28, 2017 at 10:23 pm

    Hi was wondering I have 5 guppies in a 5 gallon tank with a small bristle nose and I reacently added 3 assasin snails might this be too much because I asked the people in my local fish farm and they said not to keep more than 8 guppies thanks
    (Ps their doing very well I’m just curious)

    • Reply Mari October 28, 2017 at 10:28 pm

      Hi! Unfortunately the minimum tank size for guppies is 15 gallons. The minimum tank size for a bristlenose pleco is 30 gallons. The only thing that can actually be kept in your tank are the assassin snails; I strongly urge you to rehome the fish as soon as possible because a tank this small will not be able to handle their bioload in the long run and their lives are in danger.

      Please do not believe anyone who says there are plenty of fish species that can be kept in a 5 gallon, including your fish store. For some reason people believe fish will be happy in these tiny tanks but they won’t. I have an article on stocking a 5 gallon here and the species listed there are the ONLY ones I recommend for a 5 gal. As you can see there are only 2 fish on the list. A good stock for your tank would be the assassin snails and a pair of small dwarf crayfish like Cambarellus diminutus; they are very fun to keep and small enough to live a happy life in there.

      Sorry about the long answer – I just really hope you’ll take my advice before things go fatally wrong! Good luck with the assassins 🙂

  • Reply Kimbelry July 26, 2017 at 7:11 pm

    can i use assassin snails in my back yard pond? i am infested with pond snails!!!

    • Reply Mari July 28, 2017 at 6:22 pm

      They are tropical snails so only if you live in a tropical climate! 🙂

  • Reply Dave March 14, 2017 at 10:04 pm

    They will definitely kill large mystery snails. I got a nice big one and added it to my aquarium hoping he was big enough to resist the nerites and he was dead within hours. 🙁

    • Reply Mari March 16, 2017 at 9:12 am

      Oh, sorry to hear that 🙁 but thanks for sharing.

  • Reply Vicki January 23, 2017 at 5:27 am

    I have a 5-gallon tank. Would 5 Assassin snails be too many for my tank size? Also, do Assassin snails eat the egg sacks or just the newly hatched snails? Thanks so much!

    • Reply Mari January 26, 2017 at 11:28 am

      5 might be a bit much, 2 would be fine as well for snail extermination! They eat all kinds of organic material so they might go for the egg sacs as well, yes. 🙂

  • Reply Denny September 24, 2015 at 8:44 am

    Hello . Loved your post. please tell me, do you know if assassin snails can be fed with garden snails? Will it ruin the tank water?

    • Reply Mari September 24, 2015 at 8:57 am

      Hi! I don’t think feeding assassin snails with garden snails is a good idea, they contain all sorts of stuff the assassins won’t be used to! If you’re having trouble finding pest aqurium snails to feed them, try asking around at pet- and aquarium stores 🙂

    • Reply Ginger October 3, 2015 at 3:04 am

      hi um if you need snails please email me at [email protected] i have so many ramhorns they are extremely free

  • Reply Psybur September 14, 2015 at 1:37 am

    What the hell is that noise in the background of the video?

    • Reply Mari September 15, 2015 at 10:06 pm

      It’s not my video so I’m not sure actually, sorry! I tested it before posting and I didn’t notice anything too strange/excessively loud… it just sounds like a machine running in the background to me. Or are you hearing something completely different?!

      • Reply Psybur September 16, 2015 at 4:19 am

        Sorry, I didn’t mean to come off so brusque. I was just saying it regularly (I swear a lot, sorry). I just found it humorous that it was happening.

        • Reply Mari September 16, 2015 at 9:45 am

          No problem haha! After the incident where I didn’t notice the reflection of a naked guy’s chest in a video of a rosetail betta I was just worried maybe I missed a strange or inappropriate sound…

          • Psybur September 18, 2015 at 7:23 am

            ROFL, he’s probably in the background murmuring, ‘I’m too sexy for my shirt. . . ‘ while that’s going on! That’s hilarious; is that video still there?

          • Mari September 18, 2015 at 4:29 pm

            It’s not in the article any more, but I had a look on Youtube for you and managed to find it again here… I hadn’t even noticed it until a commenter pointed it out haha. 🙁

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