Ramshorn Snails: Pest or Helper?

Almost every fishkeeper has a ramshorn snail story. You buy a bunch of plants, and a few weeks later there are tiny flat-coiled snails on every leaf and pane of glass. Are they a problem? Usually not. Usually they're a messenger.

What they are

Ramshorn snails are small freshwater snails from the family Planorbidae, named for their flat, coiled shells that look like a ram's horn. Most stay under an inch. They come in brown, red, pink, blue and spotted "leopard" forms. They hitchhike into tanks as eggs on new plants.

Why there are suddenly hundreds

Snails only multiply as fast as the food supply allows. A ramshorn population explosion almost always means there's too much food in the tank: leftover flakes, uneaten wafers, or decaying plants. The snails aren't the cause of the mess; they're cleaning it up.

What they do for you

• Eat leftover food before it rots and spikes your ammonia.
• Eat soft algae, biofilm and dead plant matter.
• Break down waste into smaller pieces the beneficial bacteria can process.
• Tell you when you're overfeeding.

In small numbers, they're a useful part of the cleanup crew, and the colored varieties are pretty.

When they're a problem

• Thousands of them look bad and add to the waste load.
• They can nibble soft plants, especially when they've run out of other food.
• They can clog intakes and get into filters.

How to control them (without chemicals)

1. Feed less. Feed only what your fish finish in a minute or two. This alone usually brings the numbers down over a few weeks.
2. Trap them. Put a blanched lettuce or zucchini slice in the tank overnight and pull it out in the morning, covered in snails.
3. Pick them out by hand during water changes.
4. Remove dead and dying plant leaves.
5. Add a predator. Assassin snails eat other snails slowly and steadily. Some loaches eat snails too.

Avoid "snail killer" chemicals. Most contain copper, which also kills shrimp, harms other inverts, and lingers in the tank. A big snail die-off can also crash your water quality.

Don't dump them

If you're getting rid of extra snails, never dump them into a pond, ditch or stream. Some aquarium snails become invasive. Freeze them before throwing them out, or give them to someone who keeps snail-eating fish.

Keep them out in the first place

If you don't want any, dip new plants or quarantine them in a bucket for a couple of weeks and pick off any snails or clear jelly egg clutches you see. Or buy tissue-culture plants, which come in sealed cups with no hitchhikers.

In a river tank

Ramshorns are not strong-current snails. In a river tank they gather in the calm areas and on the plants and the glass at the downstream end. If you want a snail that handles flow better, nerite snails are a good choice, and mystery snails are bigger and easier to keep in check.

Sources (2)

Wikipedia: Ramshorn snail · Aquariadise: Ramshorn Snail Care Sheet

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