Assassin snails mating closeup.
There is alot of opinion written on the Assassin Snail but not alot of authority. There is a lot of folklore and a whole lot less science. Several of my aquarist friends began singing the praises of the Assassin Snail for eating other pest snails without eating plants or each other. I decided to read everything I could on them and sort through some of the conjecture and get to the bottom of these critters. I’ve decided I very much like them in my tanks.
Here are some conclusions I have come to, for now, after weighing everything I was able to find in an exhaustive web search. I gave less weight to novice keepers and those descriptions without context. I gave more weight to opinions that fit in well with other reliable opinions, were supported by other web research and by authors who could write cogent sentences.
All in all, this is what I think will shake out as a cogent profile down the line.
Assassin Snail
Antentome helena
The Assassin Snail’s common name seems to have at least 8 species under it. The taxonomy is still very unsettled. Most folks who are writing about them seem to be writing about Antentome helena and it also seems to be the most widely available.
Yes, they lay eggs but they are clear and soft unlike the Nerite snail eggs which are a hard and white and many consider an eyesore. They are laid in singles. Shrimp do not seem to eat the eggs. It seems they will lay one egg every 10 days or so and that egg should take 3 weeks to hatch and 4 more weeks to mature into full adult hood. (Edit: It seems they may lay more than one egg when they do but they don’t lay them in clumps like other snails. They lay them singly, in different parts of the tank, but more than one per cycle.)
Yes, they may eat baby shrimp if starved but definitely not under normal conditions. This is a debatable point though due to limited observation. If it has occurred, and it seems possible though unlikely, it occurs very rarely. Most observed occurrences of these snails eating shrimp seem to leave available the possibility of the snail coming upon an already dead shrimp.
They do not eat algae, however, they are attracted to algae wafers for the animal protein content.
They are usually nocturnal. Don’t be surprised if you see them tucked under a ledge or in the fold of a branch when the lights are on. They are not solely night hunters though. Seeing them during the day is common.
Four assassin snails will clear a 29 gallon tank of a massive snail infestation in 6 – 8 weeks. This number goes up drastically if you overfeed bottom dwellers. A hungry snail is a hunting snail.
Unlike many other snail species, they are not hermaphrodites or have the ability to switch gender. You need one of each for breeding. There is nothing I have found written about sexing them.
And most importantly, Yes! They will eat any sized Malaysian Trumpet Snail (MTS), Ramshorn or pond snail. An adult assassin will tank down a mystery snail many times his size if hungry. It is fun to watch them slurp an MTS out of his shell like the Assassin is doing an oyster shooter. As someone who has been overrun with MTS on more than one occasion, it is a liberating feeling.
In the US, they can be found from $2-5 each. They seem very hardy. After I buy them I drop them in a corner so that when they have left the corner, I know at some point they were alive. Sometimes, you may never see them again.
Trumpet snails on parade.
I consider these snails great friends of mine now. They have cleaned 4 large tanks of MTS and ramshorn snails; tanks I had given up on. I have not seen them breed yet but indeed that would be a huge win. Hopefully fodder for a future blog entry!
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Thank you very much, Tankgeek. You answered all my questions in “cogent sentences”. Much appreciated.
what happens after all the snails are eaten up? can the assassin snails still thrive and maybe even reproduce simply off “regular” foods?
thanks for the article!
The feed on other foods such as sinking pellets, algae wafers etc. Yes they will breed off “regular” foods.
They will not survive off algae though. They eat the animal protein that usually is in the algae wafer. They love the bloodworms and other animal based pellets you give the other inhabitants.
Thank you for this much pertinent info. Am attempting to raise an existing multitude of assassin snail young (in an established 5gal of their own, complete w/detrius. Have instituted feeding of occassional algae wafer/bloodworms. I’d had 3 adults in the tank, w/a betta & 2 catfish. Found that at least 2 adults bred very well, but proceeded to eat the young (they are now in another 5gal w/a few fish, doing well). I’m attempting this “growing” tank, & was concerned how to feed the young. I have likely 20 @ this point (that are visible). My only concern now is cleaning the tank; my thought is to leave it pretty much alone; adding water, & cleaning basic water w/out disturbing substrate. Thanks again for your help.
HEY GREAT ARTICLE. I PURCHASE 12 ASSASSIN SNAIL AND THE BEST MONEY I EVER SPENT. I PUT 6 OF THEM IN MY 125 4 MONTHS AGE AND I HAVE VERY FEW SNAILS NOW, AT FIRST ALL I COULD SEE WAS SNAILS, SNAILS, NO MORE YOU HAVE TO LOOK TO FIND A FEW. LIKE THE ARTICLE THANKS FISHMAN B
Its nice to find a decent article on them on the net , thanks
Hey! Nice article. I bought 2 assassins for my daughter’s tank as she had a snail problem after putting live plants in. So far, I have pulled out 11 baby assassins. I believe I habe found where they have laid their eggs…on the stalk of the live plant, just before the leaf starts. There are anywhere up to 3 or 4 eggs on any one stalk. I find most of the babies afternoon-evening, and if possible I take them from the main tank and pop them into a greetings net with plenty of pest snails.
I completely admired your article. Simple & to the point. I have had no luck with the eggs hatching. I found one sm completely white shell at one point, they are constantly breeding yet I have yet to see any new live Vanuatu in my 15 gal & my 40 gal tanks. I have very few rams horns left in either tank yet supplement there diet w/algee wafers and dried tubiflex & bloodworm along w/frozen brine shrimp. I guess I rely on new plants for more rams horn snails…it never fails to bring more food (rams horn worms) into my tank to feed these lil guys. 4 cleared out my 40 gal. & 4 took care of an extremely over run 15 gal tank! Wish they wouldn’t eat there young thou I will try as you suggested! Thanks again!
It actually takes 3 – 4 weeks to assassin snail eggs to hatch and after that they hide into the substrate for 3 – 8 months (usually it’s said to take about 6 months) before they reveal themselves from substrate at very first time. After that they are not even full size or mature yet, but instead something between 0.20 – 0.28 inch (=5 – 7 mm) (how fast they grow depends on water temperature mostly). Mature ones are 0.75 inches (=19mm) long, before that you won’t see any mating. In my aquarium 2 couples of assassin snails have laid over 100 eggs in month (you can see eggs in every labyrinth kind of complex surfaces, but only very few of them will ever survive to adulthood). Many others have reported same kind of results, you get tons of eggs but very few babies survive to adulthood after waiting so many months. Best results reported have been something like 2 – 15 eggs / day with 5 or 6 assassin snails.
Female is bigger and they have bigger stripes too, but difference is so tiny that it’s hard to say which one is which. When they are mating the male is riding on female for hours so you know that female is that moving one and male is that “stowaway”. Mating can even take an half of day.
They do not mate at all if there are no food including a lots of proteins. Assassin snails eat mostly smaller snails than themselves (sometimes a little bit bigger ones too), but will never attack any huge adult snails like applessnail (not even try), but will likely eat their babies. They are also not cannibals at all because they don’t eat even dead mate from same species but will eat likely any other dead snail species, after all they are carrion and carnivore.
Most snail species from this Family lives in saltwater seas, but assassin snails are completely freshwater snails, but will still survive also in brackish water conditions.
I am new to the tank group, I went big 210 gl, what I saw was something I dont understand, when the assassin leaves off a black pod type item off its back end. Is it nothing or an egg pod?
Just wanted to thank you, sooo much! I was having nightmares about the darn, ramshead snails, and have a 21″ Pleco, who is tired of the snails where he sleeps! Hoover will be soo happy! I also thank you, for giving soo much information! I had just called the local aquarium to ask about a snail infestation in my new tank, some strange looking, conch shell type snail came with some plants I got! He reccommended the Assassin Snail, so I binged & found your information! I love it! You were direct, to the point, no side chatter! You were soo much help, we are printing your info for a reference! Thank you soo much for your, VERY helpful info, just called them back & ordered 6! Your a rare spot of truth in this thing called the internet! BonsaiDi
Thank you for writing about the assasin snail. I had been fighting an infestation of snails for about a year, when I introduced 3 assasins into my 55 gallon tank. Within a month, they has taken care of the problem. they are an amazing help! I do not know how it happened, but approx, 3 monthes later we noticed our first baby assasin snail. We now have 5 more babies. I would highly recommend them to anyone that is having problems with snails.