Malaysian trumpet snails, or Melanoides tuberculata, are a perfect addition to any aquarium. They tend to burrow into the substrate, which helps shift and turn the substrate, releasing any trapped air, which helps to prevent gas build-ups in the substrate. They are great at helping to kick-start your tank's cycle as they are hardy and easily adjust to most water parameters, and they help prevent a tank from re-cycling due to lack of bio-load or large Ammonia spikes from overfeeding or decaying matter.
As long as you do not overfeed them, they will not overpopulate your aquarium.
