Niclosamide ethanolamine is suitable for the control of snails in water because of its poisoning effect by touch and stomach.

Metaldehyde lures snail and slug to feed on it. When they contact or feed on it, acetylcholinesterase is released in large quantities. 

The specialized mucus in their body is destroyed, and they eventually dehydrates and dies.

The combination of the two has a high co-toxicity coefficient.