Corals do, to some extent, require a certain quantity of light to survive. Some corals, on the other hand, rely on minerals taken from the water for sustenance rather than light.
Types of Coral Food
While many coral species have symbiont zooxanthellae algae that produce nutrients through photosynthesis from light, most soft corals, zoanthids, and gorgonians rely almost entirely on phytoplankton (small water-borne plants or algae), as well as floating detritus and slow-moving invertebrate larvae, for their nutritional needs.
Bacterioplankton, which consists of free-living bacteria and bacteria linked with decaying materials in the water (on mucus, dead plants, and other particulate matter) and is usually referred to as detritus or reef snow, is another major source of food for corals. Bacterioplankton is a major food source for almost all corals. Floating eggs, zooplankton (free-swimming microorganisms), and pseudoplankton (non-swimming creatures) are further food sources.
The fourth category of food utilized by corals is Dissolved Organic Material (DOM), which is absorbed across cell membranes directly into the coral from the water.
Many of the with bigger polyps (such as Cynarina and Catalaphyllia) are capable of collecting and devouring larger prey, such as small fish. Some corals, notably Gorgonians and soft corals, may choose their meal primarily on plankton size rather than content. Some little polyp are also voracious eaters, capturing and devouring huge prey.
If you have live corals in your aquarium, you're probably wondering what foods they eat to complement the nourishment given by the zooxanthellae algae that grow there. You may just produce a slurry of a range of different diets that span the whole spectrum and pour it into your aquarium, allowing the corals to choose what they want from the mix (the "shotgun technique" approach). However, the uneaten food in the combination will almost certainly raise your nitrate level in a short amount of time. Alternatively, you may tailor the supplement to the needs of your unique corals and use a turkey baster or syringe to apply the food straight to the coral's tentacles.
The food you feed your fish and invertebrates in your aquarium will help many corals. Meaty meals that float past or settle on corals are eaten if the food is digestible by the coral. Many corals will devour Copepods, Amphipods, Brine Shrimp, and Mysis Shrimp. Copepods and Amphipods are quite simple to grow in a refugium. In a simple DIY Hatchery, brine shrimp eggs may be born and cultivated for a low cost. Food needs for groups of corals (LPS, SPS, or soft) are difficult to generalize since each group has a few renegades with a more specialized diet. To figure out what your individual corals eat, we recommend investing in a decent coral reference book. Aquarium Corals - Selection, Husbandry, and Natural History by Eric H. Borneman is one book we strongly suggest. The sections dedicated to each coral go into great depth about what the corals eat in the wild. There's also a great section on feeding corals in your aquarium.