This is how I see saltwater tanks as being classified.
Fish Only (FO
) - Very simple name and thats what it is. A saltwater tank with just fish and a substrate of sand or crushed coral. Usually decorated with bleached coral skelitons.
Fish Only With Live Rock (FOWLR
) - The only change in this style of tank aside from a fish only tank is the addition of live rocks. Usually FOWLR
tanks also have coraline algae growth were as a Fish Only tank might not.
Reef - I would classify a reef tank to exist after adding corals to a FOWLR
tank. Other items that come along with the reef upgrade would be higher output lights and possibly an increase in flow rate above what a FOWLR
tank might have been configured with.