Good point...but corals do not really add to your bioload. Maintaining good water parameters for corals is a priority. However, if no fish reside in the tank, it is certainly a lot easier. Most corals rely on good quality light for energy. Supplementing feedings is light at best. Some nutrients are taken from the water collum but most from the proper lighting. In the properly maintained tank, corals will need to be fragged in time, this does take time. A low maintenance SW tank is a bit of an oxy-moron, but with the right amount of biological filtration, good skimming, appropriate water movement and light bioload, the work can be kept to a minimum.also the type of bioload. Corals take alot more work--you have to feed them, move them away from others, replace them according to currents and light needs, glue them back on the rocks when the jumbos knock them over etc etc.
For any SW tank using LR is about the best filtration you can get. Ideally, you want 1.5-2lbs/gal of LR, a 2-3 inch LS bed, powerheads for movement, and agressive skimming. You can a HOB if you like, but I suggest using it only for mechanical and chemial media. You only need an overflow (internal or external) is you plan to use a sump or fuge under the tank. Sumps are a great way to increase total water volume, run extra filtration and hide unsightly equipment like skimmers and heaters.So let's get to specifics. Say I want to do FISH only. Not caring about what type of fish yet, let's talk filtration. Can I go with a HOB filter or do I need to go with overflow?