Snail - Likelihood Of Harm?

It looks a bit like one of those snails called pond snails or tadpole snails or trapdoor snails or pest snails. As you can see, there is no one common name.

The most likely ones are a species of physid snail - google will give you pictures to compare to your snail.
They won't harm your fish, especially as physid snails don't grow very big - the one in your photo is quite small compared to the plant leaves.
Physids eat some algae, dead plants and fish food. They usually get into your tank as eggs on plants. They are actually a good part of the eco-systen of a tank. But if there is a lot of uneaten food or dead plants in the tank, they will multiply rapidly.