I have attempted to use a Magnum 350 for a variety of purposes and found it to be a woefully inadequate filter. As the primary filtration for a 75 gallon I think you might find it limiting. It has a very, very small basket for filter media, is designed poorly (with the impeller at the bottom it is extremely easy for the impeller to get damaged if any gravel or sand gets sucked into the filter), and compared to a Rena Filter, they are considerably louder (in my experience, even with a new impeller)