Are power heads for salt water only, or are they a good idea for fresh, 55 & 75 gal. tanks?
Powerhead can be very useful for freshwater. I use them in a pleco tank since they like a bit/lots of current as well as in planted tanks where they assure an even distribution of CO2 and ferts. And I am sure there a a few other reason :)
Just like fischkopp mentioned that power heads can be used in FW tanks or SW. But i say why the heck not use it ! My buddy had a 100 gallon FW tank, and he used power heads along with pvc to create different water flow in different areas of this tank.
It has many uses... depends what you are looking to do.
power heads are great in a freshwater tank ;D I gave mine away and I'm kicking myself for it now!
They are a great addition to a freshwater tank. The more water movement the cleaner the water, the happier the fish. I run 2 Hydor Koralia 4's in my 150 gal. and the fmy cichlids are often playing in the currents.
they are great if your fish dosent mather about the huge flow in water, cause my discus didint like that cause it was to much for them.