31-01-2021, 14:24
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All corals have four basic requirements that must be strictly observed when keeping them in an aquarium:

  • water quality
  • food
  • light
  • water movement

In general, hard corals or SPS/LPS corals are not as flexible as their soft coral counterparts, therefore mushrooms, zoanthids, polyps and leather corals are the most popular with both novices and experienced aquarists who are into reef aquariums. However, there are hard coral varieties that are actually low-demanding and adapt well to aquarium life.

LPS (Large Polyped Stony) - Rigid corals with large polyps
SPS (Small Polyped Stony) - Rigid corals with small polyps.

The following are four basic coral keeping requirements, all of which play an important role in coral well-being. However, keep in mind that certain coral species may be more finicky. Some require a wider range of lighting and increased demands on water quality. It is therefore extremely important to thoroughly investigate each individual coral species before purchasing.

Requirements for keeping corals in the tank

Water quality

  • Micronutrients in the correct concentration are required by all corals for chemical reactions necessary for food processing, growth and reproduction.
    Calcium. The minimum level is 400 ppm, the normal level is 450 ppm.
  • Strontium
  • Iodine
  • Magnesium
  • Ammonia is the most common toxin found in marine aquariums. Even in low concentrations, it causes several diseases in marine fish, invertebrates and corals. Although there will always be at least a small concentration of ammonia in the tank, it should be close to zero for best results
  • Nitrite - Ideally, this level should be zero
  • Nitrates - this should be well below 10 ppm but ideally as close to zero as possible
  • Phosphates - these should be kept below 0.3 ppm
  • pH - the allowed range is 8.2-8.4


Coral food can take many forms. Corals need much more than just light, as most of their nutritional needs are satisfied by the contents of the "soup" they live in, which contains everything - plankton as well as dissolved organic compounds in the water.


The amount and intensity of light required varies greatly depending on the species of coral and, to a large extent, on the depth at which they live in the wild. The deeper the depth, the more light is filtered in before it reaches the corals. Corals that require a lot of light cannot be found in deeper waters outside the reef.

Soft corals usually need less light, while hard corals, which live off photosynthesis, need more light.

For stony photosynthetic coral species, lack of adequate light, as well as other environmental factors can lead to coral bleaching.

Requirements for keeping corals in the aquarium

Water movement

  • Alkalinity. An optimum concentration of 3.2 - 4.5 mEq/L is considered
  • Temperature 27-29 ° C.
  • Salinity. Optimal value is considered 1.025-1.027 (specific gravity of natural seawater)
  • Zooplankton. Requirements vary according to coral species and plankton type (Phyto, Bacterio, Pseudo, Macro, Micro, Nano and Pico)
  • Dissolved organic compounds (DOC). Although some corals derive their nutrients from the decomposed organic matter suspended in the water column, excessive build up of organic compounds should be avoided as this in turn leads to nitrate accumulation in the tank. Using a good quality protein skimmer can help reduce DOC
  • Some corals require quite a strong water current to flush debris from their surface.

Care should be taken when keeping different corals in the tank. As an example, some corals do not mix well with other coral types in a closed aquarium system. Many soft corals (e.g., Actinodiscus ) should not be placed near most LPS/SPS corals as they can have detrimental effects on them.

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