We had a discussion of various canister filters on our Greater Seattle Aquarium Society (GSAS) forum and the H.O.T. Magnum got very good comments. I wanted to buy one for my 30 gallon but I didn't have the room between the back of the tank and the wall so I went with the Marineland C-160 which is doing a good job for me. Hope this helps!
I have been using a H.O.T. 350 for many years and have to say I think its a great filter! It's easy to use, clean, and does a decent job if your tank is not to big. I think a 30gal is the perfect size for it! For filter media i use 100ml bag of purigen and filter floss, once in a while i whip out the polish filter also.
ADVICE: clean it once a month and remember where the parts go! my only issue with it has been loosing the black o-rings. (which marineland sent me new ones for free)and it get a little noisy when dirty. Also a part once came unglued but is easy enough to fix and for its age understandable.