BEGINNER BASICS 14 Feb 2023 • read • Posted by Cameron Quinn in SALTWATER | BEGINNER and SALTWATER

Keeping a Reef Tank

Once the reef aquarium has been set up, the next step is looking after it.

Maintenance Schedule

Having a strict maintenance schedule is a good way to ensure that the aquarium will be successful and healthy.
A good maintenance schedule should consist of:

A weekly 10% water change, using a salt that’s appropriate for your tank.
Testing Salinity once a week.
Testing Calcium once a week.
Testing Alkalinity once a week.
Testing Magnesium once every second week.
Testing Nitrate and Nitrite once every second week.
Testing Phosphate once every second week.

Regular water changes should be able to replenish most elements if there is a very small coral population or insignificant coral growth. However, a lack of some elements may in fact be the cause of insignificant coral growth. Typically, all aquariums with corals will do better with some form of supplementation.

Daily supplementation of all elements in order to maintain the optimal parameters for your aquarium type is recommended. The daily dosage is calculated by testing each of the 3 foundation elements (Ca/Alk/Mg) on a weekly basis. This will allow you to accurately adjust the dosage according to your coral population and growth.

Reef Tank Chemistry

A successful coral reef aquarium is dependent upon maintaining the appropriate water parameters that, in turn, provide the stable environment required by the corals.

Although all the elements found in natural seawater have an important role in providing optimal water parameters, a few of them have a more significant role in overall stability. These elements are the foundation of the reef environment, and they include three major elements: calcium (Ca), magnesium (Mg), and bicarbonates (HCO3). The foundation elements are the essential building blocks of the coral skeleton.

Skeletogenesis

Skeletogenesis is the process by which special cells within the corals’ soft tissue combine the foundation elements together with strontium and barium from the surrounding water to form the building blocks of coral skeletons.

Corals build approximately 90% of their skeleton by combining calcium and carbonate ions from the water to form aragonite (CaCO3).

The rest of the skeleton is made up of magnesite (MgCO3), strontianite (SrCO3), calcite (a more brittle crystal structure of CaCO3), fluorite (CaF2), and other minor and trace minerals. In unbalanced conditions such as low levels of Mg and/or Sr the skeleton will develop with a higher proportion of calcite making it more brittle and more susceptible to damage. The foundation elements complement each other in the formation of a coral skeleton. If they are not available in the correct ratios, one of them will quickly become the limiting factor of healthy coral growth.

In addition to the foundation elements, all corals have 31 minor and trace elements present in their skeleton and soft tissue. All these minor and trace elements have an important role to play in the biology of corals (including metabolism and coloration) and are therefore depleted regularly from the surrounding water. Trace elements should be dosed according to the coral's calcium uptake in order to prevent toxic overdosing.

A reef aquarium is an artificial environment that is similar to, but not identical to a natural reef. In the open ocean, coral growth does not have a significant effect on the chemistry of the surrounding water. However, in a closed environment, such as an aquarium, the foundation elements will very quickly be depleted. Therefore, alkalinity in a reef aquarium should be kept higher than in Natural Sea Water.

Corals, depending on the species, obtain 15% to 100% of their nutrition from food sources that are suspended in the aquarium water. Using coral foods that provide a balanced mix of carbohydrates, vitamins, amino, and fatty acids that corals need, will guarantee the health and vitality of all corals. In SPS or Ultra Low Nutrient Systems, or in systems with LED lighting, higher doses of coral foods will be required.

Coral Types

Hard and Soft Coral

Hard corals are so-called because they build a hard skeleton as they grow, which is left behind when they die. Hard coral skeletons are what people used to use as ornaments in the 1970s and they are characteristically white and spiky. This type of coral is known as reef-building coral, as it's those skeletons that remain on the reef, building it up in height, before more hard corals colonise and grow on top of it. The old skeletons eventually become so encrusted, calcified, and crushed that they become rock, and that’s basically where the live rock comes from. Hard corals can build a reef.

Soft corals do contain tiny spindles inside their tissue called sclerites, which help them to hold themselves up, but these disappear when they die so a poorly soft coral may shrink and disappear completely, whereas a hard coral will always leave a skeleton behind.

LPS and SPS

Hard corals then further subdivide into LPS and SPS types. LPS stands for Large Polyp Stony and SPS stands for Small Polyp Stony. The last “S” in both can also stand for Scleractinian.

Large Polyp Stony corals tend to have very large, fleshy bodies which inflate with water and hide the skeleton underneath. Examples include Hammer, Torch, and Frogspawn corals, Scolymia, Acanthastrea, Duncan’s corals, and Bubble corals. They tend to have just one large polyp with one large mouth, like with a Scolymia, or several “heads” or polyps, like Torch corals and Duncans, with a single mouth in the middle of each head.

LPS corals are some of the most sought-after as they have amazing shapes that sway in the current and eye-popping fluorescence which shows up under blue LED light. As long as water parameters like KH, Calcium, and Magnesium are properly managed they can be quite easy to keep, as they only need medium levels of flow and light.
SPS corals are the lovely branching, tabling, and swirling-shaped corals that we imagine a pristine coral reef to look like. In contrast to LPS corals, SPS has a thin skin covering their skeleton that doesn’t inflate, and that skin is made up of thousands of tiny polyps, all with one mouth each.

SPS corals need bright light, and strong water movement and are the least forgiving of any coral. They always demand perfect water quality and many parameters must be managed including temperature, salinity, KH, Calcium, Magnesium, Potassium, Nitrate, and Phosphate.

SPS corals are seen as the ultimate challenge for many reef keepers and examples include Montipora, Acropora, Pocillopora, Seriatopora, and Stylophora. Of those, plating Montipora and Seriatopora are the easiest and should be achievable by most hobbyists. Acropora can be very unforgiving and will “Strip,” a situation where all the living tissue quickly dies off and disappears leaving only the skeleton, very easily.

SPS corals are the most vulnerable to coral bleaching events in the oceans when temperatures get too warm for them for extended periods.

If set up properly, an SPS tank is not the ideal environment for LPS and vice versa, so they are actually best kept in separate tanks for their differing needs to be met.

Numbers to Aim For:

Reef aquariums are all about keeping the water parameters within their acceptable ranges. Levels naturally fluctuate up and down constantly. For example, Alkalinity will typically rise as Calcium falls and vice versa.
Use the below numbers as a guide, but do not fall into the trap of chasing them on their up and down cycles.

Soft Coral

Soft Corals typically don’t need as high dosing due to them not having a skeleton that requires calcium or carbonate ions.

Salinity	Calcium	Magnesium	Alkalinity	Nitrate	Phosphate
34 ppt (1.025sg)	450 ppm	1350 ppm	11.5 dKH	5 ppm	0.1 ppm