My son found a snail outside and put it in my fish tank It seems to be doing ok but I want harm the Is this for snail?

Snails can live quite contently in saltwater aquariums, but not in freshwater aquariums.

Pond snails, for example, thrive in freshwater. However, pond snails can be harmful to both fish and plants in an aquarium. Freshwater snails release ammonia into the aquarium, which can be harmful to fish, and can eat plants in your aquarium, which of course is harmful to your plants!

There are some species of snails which can live in both freshwater and saltwater. In these cases, it's important to know the specific care and habitat requirements for that species to ensure its survival and well-being.

Since you don't know the species of snail your son found, it's best to remove it from the aquarium as soon as possible. If the snail is left in the aquarium, there's a higher risk of the snail laying eggs and quickly taking over the entire aquarium.