Malaysian trumpet snails are a perfect addition to any shrimp/fish tank. The snails will help prevent gas build ups in the substrate and also help prevent a tank from re-cycling due to lack of bio-load. These snails will not over populate a tank unless over feeding occurs. Snails will be equal to or larger than 1/4 of an inch. 
Please Note: Malaysian Trumpet Snails are illegal to own and purchase in Illinois and Wisconsin. Please be responsible and do not release any aquatic life into local waterways. 
Main Benefits:
Snails help keep a shrimp tank from re-cycling by provided adequate bio-load
By burrowing into the substrates, these snails help keep turn the substrate which prevents gas build up. 
Eat left over food to prevent ammonia spikes
Hardy so they can adjust to most water parameters