Saltwater aquarium lighting requirements differ depending on the type of organisms kept in your aquarium: Fish, invertebrates, or corals.
Fish-Only or Fish/Invertebrates
Aquariums with just fish (FO) require the least illumination. The lighting in a fish-only aquarium is primarily intended to enhance your pleasure of the fish. During the day, the fish just require a small amount of light. Setting a timer on your light fixture to turn it on for dawn to dark lighting in your aquarium is simple. Some light fixtures even gently turn on the light before gradually dimming it as night falls. Because many crustacean invertebrates (crabs, hermit crabs, and shrimps) and snails are nocturnal, they don't require much light in their tanks. These invertebrates can survive with simply fish tank lights.
Most aquarium kits come with enough tank, filter, and lighting for a fish-only tank. Many of these kits now feature lighting that is appropriate for soft coral reef aquariums. Kits with suitable illumination for fish-only and other aquarium types are among the best mini/nano aquariums.
Fish-Only With Live Rock Aquariums
Many saltwater aquariums use live rock as ornaments. It's a coral rock with live things like polyps and algae, as the name indicates. Because the other tank inhabitants require more light to function, FOWLR (Fish-Only With Live Rock) aquariums have a greater lighting demand than FO tanks. Macroalgae is an excellent example of something that need more light to thrive. Most saltwater aquarium owners seek to have a healthy crop of coralline algae in their tanks. The many coralline algae species not only provide color to the tank, but they also make it look more like an ocean. The growth of coralline algae is nearly totally reliant on the light it receives for photosynthesis.
Even if the initial cost of the light fixture is more than fluorescent units, the reduced running cost of extremely efficient is favorable even if the initial cost of the light fixture is higher. LED lights consume less power, so they will satisfy your demands while also saving you money.
The illumination needs for saltwater aquariums with corals, fish, anemones, and other invertebrates are the greatest. Varying corals require different amounts of light. Some soft corals, such as mushrooms and zoanthids, have lower light needs than some hard corals (LPS and SPS), which require significantly higher light intensity to grow and reproduce. Depending on the kind of coral, special illumination is necessary to guarantee that they flourish and grow.
Choosing a Tank
When fluorescent lights were the sole practical option for growing corals, along came the power compact (PC) fluorescent lights, which delivered a lot more light in a smaller fixture. Then, as "the sole light for growing corals," metal halides became fashionable. This notion was quickly dispelled when it was discovered that LEDs (Light Emitting Diodes) fitted the illumination needs of corals (intensity and appropriate spectrum) while being far more efficient than fluorescents or metal halides.
When it comes to lighting, no matter what style of tank you're building (FO, FOWLR, or reef), try to think forward. Investing in a higher-quality lighting system than you require now might save you money later on when you upgrade to a reef tank (which you will)!