Can a tank be over filtered ,freshwater .the reason I ask is my friend wants to give me a canister ehiem 2217 .I am running bio marine land pro 400.can I run all three together without any harm .or is this to much ?
I agree with the above posters, the more filtration the better as long as your fish are not being blown around the tank by the current.
If you feel the current is too strong, then there are ways mentioned in the links below to diffuse the current:
I have used Aqua Clear Brick Sponges, cut to fit and then slice an X in the sponge and slide it over the outtake area. It works great! Too, this sponge will add more housing area for beneficial bacteria. I would recommend rinsing the sponge in siphoned tank water with every water change as the sponge will clog over time .