The short answer
Pond and bladder snails hitchhike in on new plants and then multiply fast when there’s excess food in the tank. To control them, cut feeding, remove them by hand or with a trap, and add a natural predator like the assassin snail. You’ll rarely wipe them out completely — the realistic goal is to keep the population low and stable.
Why they exploded
A booming snail population is a feeding problem, not an infestation to panic over. Snails breed to match the food available, so lots of snails means there’s lots of uneaten food and waste. Cut back on feeding, remove leftovers, and their numbers naturally fall. They arrived as eggs on plants you added — see do snails eat aquarium plants for what they actually eat.
How to cut the numbers
- Reduce feeding. The most effective single step — starve the surplus and the colony shrinks.
- Manual removal. Squash or scoop the ones you see, especially after lights-out when they’re active.
- Snail trap. A blanched courgette or cucumber slice left overnight draws dozens onto it; lift it out in the morning. Repeat for a few nights.
- Assassin snails. Assassin snails hunt and eat pest snails and won’t overrun the tank themselves — the classic biological control.
Keep it in perspective
A handful of pond snails is a free clean-up crew — they graze algae, biofilm and dead leaves. The problem is only ever the numbers, and the numbers only ever come from food. Get feeding under control (see how often to feed), add a couple of assassins if you like, and the tank settles into balance.