Sometimes too much water circulation may bother certain types of fish, and the plants will start bending along with the water current. If you are able to reduce the amount of flow when needed, then there should be no problem.
they say to get a filter that will turn over 4 times as much water as that in ur tank an hour.......so if its a 40 ltre tank u want ur filter to pull thru at least 160 litres an hour......but anythin more is okay