Is it normal for a penguin 350 biowheel filter to be noisy? Like a clearly audible HUMMing sound?
The bio wheels will make some noise, however it shouldn't be making a very noticeable humming sound as you put it. I had 2 on my 75g. The Aquaclear's are a very solid product and they are very quite. You just may have to remove the top from the filter.
"When creating an aqua scape, strive for the beauty of imperfection, as its art and there is no wrong or right, it's left open for interpretation" James Findley
Yeah, I got it used, WITH a tank, and thought, Oh great, free filter! But I suppose not.
The filter or the motor?
The motor. Most LFS carry replacement parts, but they keep them off the main floor most of the time so just call around and ask if they have a new motor for your model. Even if they don't have it its something they can order, and its a lot cheaper that replacing the entire filter. First check the impeller tho. If the magnet looks really scored up you may wanna start with just that then. If that magnet isn't smooth it makes a ton of racket. The impeller on my magnum 350 is going and it's starting to get pretty noisy.