Snails in the Aquarium

Introduction

Ask ten fishkeepers about snails and you will get ten different opinions. To some they are invaluable algae cleaners and fascinating tank inhabitants; to others they are unwanted hitchhikers that multiply out of control and consume plants. The truth is more nuanced than either camp suggests, and understanding the difference between the various snail types that appear in aquariums makes a significant difference in how you manage them.

Quick Overview

Beneficial Pest Snails

The most common "pest" snails that arrive uninvited on plant tissue are actually beneficial to a well-run aquarium, and the hobbyist community has largely come to recognize this.

Bladder Snails and Pond Snails

These small, teardrop-shaped snails (typically under 1 cm) arrive on plants purchased from most fish stores. They are prolific reproducers under good conditions and populations can seem overwhelming if feeding is heavy. But they eat algae, consume decaying plant matter, and help break down leftover food before it rots in the tank.

Population control is simple: snail numbers track food availability. Reduce feeding and allow algae growth to level off, and snail populations shrink accordingly. They are not a problem to be eliminated; they are an indicator of overfeeding or decomposing matter in the tank.

Malaysian Trumpet Snails (MTS)

Malaysian trumpet snails are cone-shaped, sand-dwelling snails that spend most of the day buried in the substrate, emerging at night to graze. Their burrowing activity aerates the substrate and prevents the buildup of toxic hydrogen sulfide gas in deep sand beds. They are almost universally considered beneficial in planted tanks and are deliberately introduced by many experienced hobbyists.

Malaysian trumpet snails are almost impossible to eradicate once established without a complete tank teardown, and they reproduce rapidly in warm, well-fed tanks. If you do not want them, do not introduce them. If they are already present, focus on population management through reduced feeding rather than elimination.

Deliberately Kept Snails

Nerite Snails

Nerite snails are the gold standard algae-cleaning snail for aquariums. They eat green spot algae, diatoms, hair algae, and film algae from glass, substrate, and plant leaves with remarkable efficiency. They do not eat healthy plant tissue. Crucially, nerites cannot reproduce in freshwater, so they never overpopulate, though they do lay small white eggs on hard surfaces that are harmless but can be unsightly.

• Zebra nerites, tiger nerites, horned nerites, and olive nerites are all effective and attractively patterned
• Add 1 nerite per 5-10 gallons as a guideline; they need adequate algae growth to sustain themselves
• They are escape artists; ensure the tank has a tight-fitting lid with no gaps

Mystery Snails

Mystery snails (Pomacea bridgesii) are large, attractive snails with shells up to golf ball size, available in golden, blue, purple, ivory, and other color morphs. They are peaceful, charismatic tank inhabitants that eat algae and decaying plant matter. Unlike pest snails, they reproduce only from separately laid clutches of eggs above the waterline, which are easy to remove if you do not want them to hatch.

Ramshorn Snails

Ramshorns arrive as pests but are also deliberately kept in larger, more colorful varieties. They eat algae and decaying matter, are attractive when kept in the red or pink color morphs, and populations respond directly to food availability. They are popular food items for pea puffers, assassin snails, and some loach species.

Assassin Snails

Assassin snails (Clea helena) are small predatory snails that hunt and eat other snails, making them an effective biological control for pest snail outbreaks. They reproduce slowly enough that they do not themselves become a pest. They are attractive, with yellow and brown banding, and make interesting tank inhabitants beyond their pest-control role.

Snail-Eating Fish

For tanks where snail populations are genuinely out of control, snail-eating fish are an alternative to chemical treatments (which should be avoided, as most "snail kill" products harm invertebrates broadly and pollute the tank).

• Pea puffers: enthusiastic snail hunters; keep with caution as they are also fin nippers
• Clown loaches: love snails but grow large (12 inches) and need a large tank long-term
• Yoyo loaches (Botia almorhae): smaller than clown loaches, effective snail hunters, active and entertaining
• Assassin snails: the invertebrate option; slow but methodical