The best optics toward aquarium keeping is that taking care of your fish means achieving great water quality.
Depending on the type of aquarium you purchase, it may or may not be a “reef ready” tank. Reef ready means it has been drilled in specific places on the glass bottom and overflows with slotted weirs glued into corners or along the back. In a peninsula style tank, the entire side wall may be an overflow. The drilled holes are fitted then with bulkheads and flexible or rigid piping to a sump is routed to the sump and then back from a submersible pump to the tank. Sumps provide plenty of space for surface area filtration (both physical and biological) and space for a protein skimmer.
Canister filters are the next best choice for your aquarium, if you are not purchasing a reef ready tank. They offer a variety of crucial filtration methods in the most practical layout. Filtration is made up of physical filtration and bio-filtration. Physical filtration consists of pads, sponges, and sometimes carbon to filter particulate. Bio-filtration, however, utilizes media that houses important nitrifying bacteria required to remove toxic ammonia from the system. This media is typically included in canister filters. For smaller tanks, hang on back protein skimmers can be purchased as well.
Finally, a hang on back (HOB) filter may also be used on tanks that are not “Reef Ready”. They employ the same mechanical and biological filtration medias as sumps and canister filters, but are more compact.
Turn off return pump or canister filter when feeding. This will help to extend the life of your filtration media, avoid wasting food, and creating more waste to break down in your tank. Remember, what goes in to your marine aquarium must come out some how.
General rule of thumb for any marine tank is turning over the complete volume 5 to 6 times per hour.
A flow rate of between 4-6 times the gallons per hour (depending on bio-load) is required to adequate filtration. So, for a 20 gallon (75.7 L) tank moderately stocked, a filter with a 80 gallon-per hour flow rate (303 L per hour) would suffice. A heavily stocked tank of the same volume would require a 120 gallon-per-hour (454 L per hour) flow rate.