ok cool thank you i was worried some of my coral did not like it and my clownfish and other fish was to weak to swim with that currentI have that size in my 20 gallon quarantine tank. The tang in there now loves it he swims straight into it but doesn't actually move. It works like a treadmill for fish. Sometimes you will have to move coral that doesn't like so much current but most like at least moderate current and many like a lot of current.