There are many culturing techniques, but all need three key ingredients: Substrate Substrate or base rock, are terms referring to the dry rocks that will be exposed to saltwater to get colonized and form Live Rock. Rock aquaculturists prefer to use calcareous media because its high content of calcium and magnesium carbonate, which helps to balance alkalinity and to buffer pH. Although calcareous substrates are preferred, it is important to clarify that other non-calcareous media can also be used... the only constrain is that substrates cannot contain substances that are toxic to aquarium species. Non-calcareous Live Rock would not have the alkalinity balancing and pH buffering benefits, but could certainly deliver all other benefits.
The large majority of aquaculture operations use two types of substrates:
2. Conglomerated substrates are made by mixing cement and granular media (like sand and gravel). Sometimes aquaculturists also add "porosity-enhancing agents", which are granular material (most often salt) that dissolves away when submersed, leaving voids in the substrate. Although sometimes used in commercial enterprises, conglomerated substrates are most often made at home in small quantities by aquarium hobbyists, therefore this type of substrate is often referred to as "DO-It-Yourself" substrate or DIY rock. Most people use calcareous media like aragonite sand and crushed oyster shells. The "porosity-enhancing agents" can be a number of different materials that dissolve or break down in water, like salt grains, clay pellets and pasta noddles. The most often used cement is regular Portland cement, although white cement and quick-set cements are also used. Different people used different ratios of cement, calcareous media and water-soluble materials. Too much cement makes the end product too dense... and too much water-soluble materials may make the end-product brittle and easy to break. ALL conglomerated substrates that use cement need to be "kured". Cement hardens by a hydration reaction that produces Calcium Hydroxide as a by-product. Calcium Hydroxide (also know as lime or “Kalkwasser”), which is an additive commonly used in saltwater aquaria to replenish calcium used by corals and to raise pH. However too much calcium hydroxide can over-increase pH in you tank potentially harming aquarium organisms. Substrate made using concrete to be submersed in water (with very frequent water changes) to allow the calcium hydroxide to leach out of the rocks. This process is called "kuring" the rocks. Saltwater and Seed organisms  Substrate need to be submersed in seawater to allow bacteria and other organisms to colonize it. This can achieved by placing the substrate directly in the ocean or in a tank with some "seed rock". Ocean-cultured Live Rock.- Substrate is place directly into the ocean, either on a sandy area somewhat close to a coral reef or in a shallow lagoon. The deployment of substrate in the open ocean is often conducted from a floating barge with a crane (see figure). Substrate deployment in shallow lagoons can be done from small crafts or by foot. Ocean aquaculturists may have to apply for government permits. The main benefit of ocean-cultured is that
rocks are harvested with high-diversity and high-biomass of colonizing
organisms... same as wild-harvested Live rock but WITHOUT the
destruction of coral reef habitat. The main disadvantages are:
Tank-raised Live Rock.- Substrate is placed directly in tanks that contain "seed rock", which are pieces of Live Rock with beneficial bacteria, encrusting coralline algae and other invertebrates. The idea is that the organisms from the "seed rock" will spread and colonize the substrate. This is a common practice used by hobbyists starting a new tank, but there are also commercial enterprises. The main advantages of tank-raised Live Rock are:
The main disadvantage is that tank-raised Live Rocks often comes with less organism diversity and with less hitchhikers. |
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