What is the snail that cleans fish tanks i have heard of it somewhere?

You may be referring to the Malaysian Trumpet Snail (MTS), which is a small freshwater snail that is often used in aquariums to help clean the tank and control algae growth. MTS are known for their burrowing behavior, which helps to aerate the substrate and keep it clean. They also feed on detritus, algae, and biofilm, which can help to keep the water in the tank clean. MTS are generally considered to be safe for fish and plants, and they can help to create a more natural environment in the aquarium.