The flow of water set on the basis of the types and size of the aquarium. There are different types of filter per feed require to manage the 300 or more GPH per inch depends on the level of the aquarium. There are more capacity filters are also available in the different capacity right from 300 to 1200 GPH.
The water flow is double depending on the capacity of the filter. It is necessary to move the water in the tank so that the fish can get the fresh water in the water tank.