Here's the scenario: You've got the "bug" and you're going to set up another, larger fish tank, or you're going to replace your existing tank with a larger one. You've always used HOB filters (commonly called box filters), but you're considering a canister or two for the filtration on your new tank. The problem is you've never used a canister, and you don't really know much about them.
There are plenty of other resources available that describe how canister filters work, what types and amount of media they hold, and what makes them different from other filter types. So I won't go through all of that here.
If you're a member of an online cichlid forum or a Facebook cichlid group, you might ask for opinions on what to buy. This is a great way to learn what equipment other hobbyists are using. It's also a great way to get some bad advice. Many hobbyists choose to be frugal when it comes to buying equipment, either because higher priced hardware don't fit their budget or they just prefer to go the inexpensive route.
Be a little extra weary of going the inexpensive route with your filters. Actually, I recommend that you consider spending a little more and purchase a higher quality brand. Sure, even the higher end canisters fail sometimes. However, the probability that you'll experience a problem with some of the cheaper brands is greater, and those brands won't have as strong a warranty. Look for filter warranties in the 2-3 year range. I won't disparage any brands here on the blog, but some are clearly more cheaply constructed, which means they'll experience a failure of some type more frequently. Furthermore, in my opinion, spending a little more lessens the likelihood that a simple plastic component in your filter breaks within the warranty period.
The Cichlid Room Companion
Tropical Fish Hobbyist
American Cichlid Assoc.
African Cichlid Hub