Pond snails can be a beautiful addition to your pond’s ecosystem. Pond snails can be a fun & interesting addition to your pond’s ecosystem. In very large ponds, snails can even be necessary to create a balanced, natural ecosystem. I’m very fond of snails, certainly.
However, I do think that how much snails improve the health and clarity of the average pond has been blown out of proportion. The wisdom is generally that pond snails eat algae and some organic debris. They’re the little scavenging janitors of your pond. In a well-kept pond, though, I disagree with this view. Certainly, pond snails will get rid of some algae in the pond, and some of the debris. However, they will not have a significant effect on the problems that most pond owners face with water health. They won’t help with green water. The planktonic algae whose blooms cause green water are too small and free-floating for snails to eat them. In fact, snails may make this problem worse, as they will feed mostly on the healthy slime algae that prevents planktonic algae blooms.
Snails also won’t help significantly with one of the most common problems I see in ponds, an overabundance of pond sludge. Now, snails will eat some of the organic debris that makes up your pond sludge layer, but I’ve found that they far prefer the healthy slime algae that actually helps keep your pond clean. Thus, too many snails can make the pond sludge problem grow, rather than get better. Further, pond snails tend to breed quickly, and too many snails means dead snails that become part of the sludge instead of eating it up.
Snails might help if you’ve got a bad string algae problem. However, they’ll prefer to feed on the slime algae that actually helps to use up the nutrients that string algae feeds on. If you’re looking for an easy fix for string algae, there are better ways than snails.
So, snails aren’t the natural, effortless pond janitors that you might be looking for. They’re still very pretty and interesting, so I won’t try to talk people out of putting them in their ponds if that’s what they want. For my part, though, I don’t add them to my ponds. I’d rather have the slime algae.