tank predominantly concentrates on the display of saltwater fish. As such it is a much more forgiving environment as compared to the true reef tank. Lighting requirements, water quality, water chemistry, filtration and flow are much more demanding in the true reef tank. There are several different categories of corals that each have different lighting requirements.
The reef tank focuses much more on coral rather than fish (plus your fish selection is limited to those species that won't eat your expensive coral).
Many of us end up with the hybrid. FOWLR
with 'reef' inhabitants that will survive based the equipment and fish/inverts we have in out FOWLR
The hobby progression is typically freshwater - saltwater FOWLR
- saltwater reef. With each becoming more advanced, difficult and expensive.