Cichlids, especially the bigger species, tend to produce an enormous amount of waste. Hence most recommendations regarding the filtration of community tanks won't hold for cichlid tanks.
External filters products
External filters products that you can buy at every fish store are quiet, easy to setup and maintain, but do cost quite a lot of money. If you can afford it, it's a good solution, but don't follow the recommendations regarding tank size (see above): If you are going to use an external filter for a tank with mainly cichlids, choose one that is suited for tanks twice the size of your tank.
Internal filters products
The best and cheapest solution for smaller tanks.
Internal filter products are cheaper than external filters, but on the downside they take room from the tank tiself. Also, they might be harder to clean, depending on your light setup which you might have to remove to access the filter.
A good and extremely cheap alternative to commercial products are so called "sponge filters", simple internal filters consisting of filter media and a tube only, driven by either an airpump or a powerhead. Since the size of the filter media (the "sponge") can scale with the tank size, this filtration can be used in tanks of arbitrary size.
Sponge filters are great for grow-up tanks for juveniles, because fries can't be sucked into the filter. However, the airpump and the resulting bubbles are quite loud and may limit your living room experience.
- The well known site "The Krib" has archived Usenet postings about sponge filters
- Another DIY sponge filter.
- And one more site.
Sponge filters XL - "Hamburg mat filters"
In Germany the idea of the engineer (Dipl.-Ing.) Olaf Deters has spread in the German part of the aquaria community for the past decade. He has posted his description of a simple and cheap, but extremely (and proven) powerful filter type to the Usenet back in 1996 and has continued to work on it since then. Since then the so called "Hamburg mat filters" (Hamburger Matten Filter, HMF) are a well-known term and used by many hobbiests.
The basic idea is similar to the regular sponge filters mentioned above. But he is using big filtration mats to reach a much higher filtration volume. He has done some analytics and maths about optimal filtration size for best possible biological decomposition of toxic substances.
All you need is a powerhead and a big mat of filtration media, that you can usually buy at every aquaria store. As you can imagine this is a very cheap solution for tanks, and you can save a lot of money. The filtration media (the mats) are usually blue or green and don't look very natural in the beginning, but over the time algae will grow on the media and give it a natural look.
Unfortunately the original homepage is in German only, but there are a lot of good pictures and schematics, so I'm sure you can get the idea if you want to build one yourself.