An aquarium with good water flow will result in a healthy ecosystem. Most importantly, water circulation helps with gas movement and filtration. Gas like carbon dioxide, CO2, produced by fish, is moved around in the aquarium. There is other gases form bacterial break done of waste that moves around. Waste particles are driven around by water movement and then go into the filtration system. If there is no movement, there would be concentrated pockets of gas and waste that will be harmful to the aquarium ecosystem.
Pumps do water circulation immerse in the aquarium. The size of the aquarium will determine the power of the pump to use. Since there are so many to choose from, please get information on the right fit for your aquarium.
On this site, you will find a variety of pumps with similar functions. Also, a range of accessories are available for parts replacement or to add on to your pump.