I normally provide the below information in relation to the Magnum 350 canister, but the concept remains the same. The Magnum HOT is a well made, long life filter. Many do not like them because of the absence of bio-filtration and they are designed specifically for carbon filtration. However, a couple of simple mods turn the HOT into a great little filter. In addition, because of it's no media bypass design, it is much more efficient than most filters in it's price class, which allows them to be more effective, if modified, than other filters in the same class.
The Magnum HOT can be converted into a super little filter with only a couple of simple mods. First, get an extra blue bonded filter sleeve and wrap two sleeves around the media container.
Second, get a reverse flow kit for a Penguin powerhead and attach the strainer/foam pre-filter from the kit to the inflow tube of the Magnum. This improves mechanical filtration and makes the bio-media (below) more effective.
Third, take the media container and toss the carbon. Fill the media container with either Hagen BioMax or Eheim Ehfisubstrat.
Right now, you can get the Magnum H.O.T. Pro for $59.99at DrsFosterSmith.Com.