Hang-on-Back filters have one real advantage: they’re cheap. After that, they’re mainly noisy, messy and bulky. Canister filters are a great improvement on them; they’re quieter, cleaner and easy to hide away. They do have one big disadvantage though, cleaning them can be a bit of a chore. To clean a canister filter properly you’ll need to disconnect it from the aquarium, being careful not to lose siphon. Then you’ll locate to a place where you can make a mess, before undoing a bunch of clips and diving into the layered medias within.
Between these two though there is a middle path, the Middle Way of freshwater filtration, it’s a path less traveled but worthy of more attention. This is the realm of the in-tank filters, such as Tunze’s Comline series.
Here we see two of the Comline filters. All of the Comlines are linkable. This let’s you use the motor from one to provide water flow through all of them.
With this style filter everything is enclosed in an unobtrusive box inside the aquarium. Locating them in a back corner makes them blend right in. They run absolutely silently. And perhaps their biggest advantage is the ease with which the media can be changed and cleaned. Inside are located the plug-and-play cartridges pictured below. These can be filled with whatever the aquarist requires. depending on the aquarium style and inhabitants.