If you are looking for a filter for a 35 60 gallon tank, this is the one for you.
I run this filter on my 46 gallon planted aquarium, and love all the things you can do with it. On a normal filter, you have one slot for a filter cartridge. This one has four slots. It comes with two grey filter cartridges that come open at the middle, allowing you to put extra charcoal, filter floss, etc in it. You get two of those and two regular cartridges. The cartridges that it uses are somewhat expensive, but can be found inexpensively on the Internet.
First try www.petsmart.com , and go from there. This filter has two biowheels. These are wheels of material that get a spray of water from a spray bar on them. They quickly grow a huge mass of biobugs, and over time you can physically see the color go from white to the desirable brown, which are the bacteria, constantly soaking up ammonia and nitrate. When I set this tank/filter up, I never saw an ammonia spike and the nitrite spike was easy to sail through and only lasted a couple of days.
This filter comes with two biowheel spray bar combos. I have had this filter running for a while now, and it still remains silent. The only thing I don't like about it is when one of the dinky little invasive snails dies. Sometimes (ok it happened twice in a year) a snail will die, and the shell will fall down into the impeller. It is then your job to get the thing out before it tears up the motor/impeller. This is sometimes hard because of the way it is designed.
Don't let this stop you from getting it: This filter still remains my favorite filter to this day. This filter is very easy to clean, requiring minimum maintenance, one a month. The Marineland Emperor 400 is the ultimate HOB filter: not as expensive as a canister, but with all the options and much more easy to use.
Written By AJB
Comment By: jaimecid BIO-Wheels are the best. I have a Penguin Emperor 400 for a 30 gal tank....simply the best, the sound is nice and soothing...and the oxygenation bacteria get is unsurpassed, even by canisters....which are better mechanically, but only on tanks 40 and over. For a 40 or under, a HOB is the best, and a BIO - Wheel is a must, even for those larger tanks with a canister....because the BIO-Wheel Air oxygenation of bacteria can not be achieved by the water oxygenation of the bacteria by the enclosed wet canister.