Available in 5 sizes, Penn Plax offers the Cascade series of canister filters. Designed for aquariums from 30 gallons to 200 gallons, the Cascade filters pretty much follow the template for building a user friendly canister filter. The motorhead locks onto the canister body with large lock down clamps, and the o-ring is recessed in position. The inlet and outlet tubes connect to the motorhead with removable shut-off valves, and there is a priming pump button to restart the water flow. The canister body has 2 to 5 media baskets to fill with the various types of media. At the very bottom, Cascade uses a Bio-Sponge to act as the first stage mechanical filter and to also offer surface area for the beneficial nitrifying bacteria. They also offer a finer mechanical pad called the Bio-Floss, one for each media basket. For chemical filtration, they offer a Pro-Carb Activated Carbon mesh bag to be placed in one or more of the upper media baskets. Unfortunately, the Cascade canister filter does not come fully packed; there is room for more chemical media and biological media, like the Bio-Rings Ceramic filter. For freshwater applications, they also offer the Pro-Z Zeolite Crystals to control ammonia, and a mix of the ammonia removing crystals and activated carbon called Pro-Carb +Z. The Cascade is one of the few canisters with a built in carrying handle to facilitate carrying it to the sink for maintenance.
The AquaTop canisters are available in two different modes, the CF canisters and the newer design AquaTop Self Priming Canisters. Both series include a UV sterilizer built into the canister to help control bacterial infections and free floating algae. The CF series uses a 9W bulb, and the Self-Priming uses a 5W bulb. Other than the UV system, the AquaTop canisters are very similar to all the other canister filters using large clamps to hold the motorhead to the canister body and disconnects for the intake/outlet hoses. The canister body has media baskets to hold the various media. The units come with one Coarse Filter Pad for the bottom chamber and one Fine Filter Pad for each basket. They also include one carbon pad for chemical filtration. This leaves more room for more types of chemical media, like BioChem-Zorb or Chemi-Pure, and extra space for one of the ceramic-type bio-media rings. Unique to the Self-Priming series of canisters is the self-priming pump built into the motorhead. With a simple push of a button, you turn on a vacuum pump to draw in the water through the intake hose and fill the canister. Once it is filled, the pump turns off automatically, and you can start the circulation magnetic drive pump. The UV bulb will require replacement after 9 to 12 months of continuous use to maintain a proper kill dose to eliminate pathogens and free floating algae.
One last canister to discuss is the fairly unique H.O.T. Magnum canister from Marineland. The Hang On Tank (H.O.T.) is designed to be placed directly on the back of the aquarium and, in place of long intake/return tubing, uses rigid pipe intake stems and an outlet deflector to circulate the water in the tank. This compact, efficient design allows the hobbyists to have the benefits of a canister filter (no by-pass, quiet operation, less evaporation, more media volume) without the clutter of the hoses. The canister comes with two styles of filters, the Micron Cartridge for really fine, occasional cleaning and the everyday use Media Container and foam sleeve. The Media Container works well with the Black Diamond carbon or with other resin media if they are in a mesh bag. The impeller is located near the bottom of the canister, making this unit capable of self-priming if you fill the canister with some water during cleaning. The lid locks into place with a clamp mechanism and uses an adjustable metal hanger to fit most sizes of aquarium trim. If you also want the system to offer biological filtration, you can purchase the H.O.T. Magnum PRO system that includes a Pro BioWheel connected to the outlet of the canister.