some people like them, I honestlly hate them. My reasoning for that is they use those stupid inserts for filter media. They plug like crazy and can only be replaced as a whole and not piece by piece. If you want to use a HOB I only, only, only buy Aqua Clear. I swear by the 70 and the 110. I can pack all the media I want and can wash some while leaving some in their. This way my biological filter is always in good shape. I will argue againts anyone when I say that two AC 110's will out filter any canister filter. My two cents