Assassin snails have a reputation as predators, but several fish, invertebrates, and even other assassin snails will eat them. If you’re trying to control an assassin snail population in your aquarium, or simply want to keep them safe from tankmates, knowing their predators matters.
Loaches: The Most Common Threat
Loaches are the predator most aquarium keepers encounter first. Clown loaches, yoyo loaches, and other members of the loach family are dedicated snail eaters. They use their narrow mouths to pull snails from their shells, and they don’t discriminate by species. Assassin snails are fair game alongside pest snails.
That said, the interaction isn’t always straightforward. Some fishkeepers report that loaches will damage assassin snails but then leave them alone afterward. One theory is that assassin snails may release a toxin or use their venom as a deterrent, making loaches lose interest after an initial attempt. Smaller loaches may struggle with adult assassin snails, whose shells are thicker and more elongated than typical pest snail shells. Larger loaches, particularly clown loaches that grow to nearly a foot long, have little trouble.
Pufferfish Can Crush the Shell
Freshwater pufferfish are built to eat snails. Their fused, beak-like teeth are specifically designed to crack through shells, and they actively hunt snails as a primary food source. Dwarf pea pufferfish will go after smaller assassin snails, while larger species like the Amazon puffer or figure-eight puffer can handle adults with ease. If you keep pufferfish in a tank, no snail species is truly safe.
Large Cichlids and Other Aggressive Fish
Big, aggressive cichlids will harm or eat assassin snails. Species like oscars, Jack Dempseys, and larger African cichlids have the jaw strength and the temperament to crack into snail shells or simply crush them. These fish are opportunistic feeders, so while they may not specifically hunt assassin snails, they won’t pass up an easy meal crawling across the substrate.
Crayfish Will Eat Them
Freshwater crayfish are a serious threat to assassin snails. Crayfish are strong enough to hold a snail and pry it from its shell, and they will almost always eat any snail they can catch. This applies to virtually all crayfish species kept in aquariums. If you’re keeping assassin snails to manage pest populations, adding crayfish to the same tank defeats the purpose since the crayfish will eat the assassin snails right alongside everything else.
Assassin Snails Eat Each Other
One of the more surprising predators of assassin snails is other assassin snails. They are confirmed cannibals. Aquarium keepers have reported finding smaller assassin snails completely emptied from their shells, with no other explanation than predation by their larger tankmates. The smallest snails in the group are the most vulnerable, particularly juveniles that haven’t yet developed a thick shell.
This cannibalistic behavior actually serves as a natural population control. When food runs low (typically after they’ve wiped out the pest snail population you bought them to handle), assassin snails will turn on each other. Smaller, weaker individuals get picked off first. If you started with a group and notice the numbers slowly declining even though nothing else in the tank should be eating them, cannibalism is the likely explanation.
What Keeps Them Safe in the Wild
In their native habitat across Southeast Asia, assassin snails are non-selective predators and scavengers. They eat a wide variety of other snails, including species larger than themselves, and will also feed on fish eggs and shrimp. Their elongated, striped shell offers some protection, and they spend much of their time buried in sandy substrate, which helps them avoid detection by predators above.
Their burrowing habit is worth noting for aquarium keepers too. Assassin snails frequently disappear into the substrate for days at a time, which can make it hard to tell whether they’ve been eaten or are simply hiding. Before assuming a predator got them, check whether they resurface after a few days. They’re surprisingly good at staying out of sight.
Choosing Safe Tankmates
If you want to protect your assassin snails, avoid housing them with loaches, pufferfish, large cichlids, or crayfish. Peaceful community fish like tetras, rasboras, corydoras catfish, and gouramis pose no real threat. Shrimp are generally safe tankmates as well, though assassin snails may occasionally go after very small shrimp if they’re hungry enough.
If your goal is the opposite and you want to reduce an assassin snail population that’s gotten out of hand, a few loaches are your most practical option. They’ll gradually thin the numbers without the aggression issues that come with cichlids or the specialized care that pufferfish require. Alternatively, you can simply reduce feeding in the tank and let the assassin snails’ own cannibalistic tendencies bring the population down over time.