Newb question about GFO reactors

[Oceansize]

I'm looking into GFO reactors, and the one I have my eye on (Aquamaxx) seems to imply that if you don't have a sump, you need to purchase a HOB bracket and hang the reactor over the side.

This confuses me. As long as I've got the right-size return pump, shouldn't I be able to put the GFO reactor under the tank next to my other reactors (denitrator and calcium)? Why would it need to go into a sump?

Neither my denitrator nor calcium reactor require a sump or HOB. What makes a GFO reactor different?

Or am I simply misreading the description?

 

[AlexStinson]

I would assume that would be fine, they probably assume you are running it off a powerhead connected close to it.