Reef Aquarium keeping: Requirements of corals and marine invertebrates
Invertebrates, especially corals, have more specialized needs than marine fish, and these must be considered if a reef tank is to be effectively maintained.
The first and most important necessity is high-quality water. Because invertebrates tolerate a smaller range of pH, salinity, and temperature than marine fish, values must always be maintained near the optimums. Even more concerning is the quantity of trash present, particularly nitrate. While fish are generally tolerant to nitrate, most invertebrates are not and begin to suffer at levels as low as 20mg/l. Keeping nitrate levels low is one of the most important factors to consider when setting up a reef tank, and it is the major reason why fish populations in a reef must be regulated. Invertebrates, on the other hand, are somewhat more tolerant to ammonia and nitrite than fish, which is why living rock is occasionally employed in cycle aquaria. Invertebrates are also very sensitive to dissolved metals (especially copper) and practically all aquarium treatments. If the tap water includes a significant concentration of dissolved metal, it is strongly advised to filter it via activated carbon before consumption. Because relatively few pharmaceuticals may be used in a reef tank, it is even more important to maintain good water quality, as this provides the fish with more disease resistance. Disease prevention is one of the reasons why UV sterilization and the use of ozone are more common in reef systems than in fish-only systems, however, ozone has additional advantages as discussed below. While these steps help avoid fish illness, having a separate fish-only quarantine tank is an excellent idea whenever space and money allow.
Lighting is the second need of many (but not all) invertebrates. Although they are animals, virtually all corals sustain photosynthetic algae inside their tissues and depend on them for food and energy, but not solely. Although hard or stony corals are well recognized for this, numerous anemones, soft corals, and other invertebrates such as clams also utilize these specialized algae. Furthermore, attractive macroalgae, like other aquarium plants, need light and nutrients to flourish. The intensity and spectrum of light are equally significant. Because water absorbs red light, the spectrum that reaches the coral is bluer than the light that touches the surface in the tropics. While terrestrial and freshwater plants require mostly red light (with some blue) for photosynthesis, corals and the majority of marine algae are blue-adapted and do not need red light. Reef tanks, as opposed to fish-only systems, need more light and probably more specialized lighting to give adequate light intensity and spectrum. More information regarding lighting choices may be found here.
Corals, as previously stated, do not solely feed on algae. They also collect food by grabbing plankton (small floating organisms) in the water and scavenging off rocks and sediment surrounding them using unique feeding tentacles. These strategies are used to varying degrees by different coral species. Some corals depend significantly on algae and need a high light intensity, while others rely on it very little and hence do not require as much light, but should be fed with alternative food. Anemones, in general, depend less on light than coral and grab most of their prey with their sticky tentacles. Certain clams, on the other hand, need intense light and depend substantially on algae stored in their tissue. Of course, there are invertebrates that have no need for light at all, such as crabs, snails, starfish, urchins, and a variety of others. If these species are more appealing to you than corals, then light is not an issue, but keep in mind that they still need extremely excellent water quality and low nitrates. More information about the many varieties of invertebrates and their individual needs may be found here.
Water flow is the third issue for many invertebrates. In addition to the energy they acquire from their algae, many corals and anemones grab tiny floating creatures or other particles as food. A variety of different invertebrates rely only on the collection of suspended plankton for nourishment. Filter- or suspension-feeders are animals that acquire all of their food from particles caught in the water. These include numerous relatives of corals and anemones, certain polychaete worms, sponges, bivalves, and a variety of others. Because many of these species are stuck to rocks and cannot move, it is critical that there be enough water circulation to feed them with food. Water flow that is excessively powerful, on the other hand, might be harmful since it can hurt them or just move food by too rapidly. Water movement is extremely crucial for corals, not just to provide them with more food, but also to keep their surfaces free of mucus, debris, and algae. Good water flow is also essential for getting the most out of the helpful microorganisms that colonize reef aquariums.
Fourth, invertebrates have different feeding and nutritional needs than fish-only marine tanks. Filter-feeders in particular need special feeds – brine shrimp is good for some, and there are also prepared foods with a suspension of tiny nutritious particles. Another factor to consider is vitamins and minerals. While fish obtain their vitamins and minerals from food, many invertebrates, especially corals, get them from the ocean. Corals need calcium and a variety of other minerals to form their skeletons, and these must often be supplemented to guarantee an appropriate supply. Macroalgae may also need additional nutrients to boost development; however, particular products should be used to avoid adding unnecessary and potentially harmful chemicals.
Finally, if a reef is to be effectively maintained, the fish must be compatible with the corals and other invertebrate species that will be retained. Fish that devour corals should be avoided, such as parrotfish, triggerfish, numerous pufferfish, giant angelfish, and butterflyfish. Furthermore, predatory fish that create a considerable quantity of waste is not typically suggested since corals and other organisms cannot deal with the high nitrate levels that ensue. Clownfish, damsels, dottybacks, gobies, blennies, hawkfish, numerous tangs and dwarf angels, and some wrasses are examples of reef-friendly fish. Fish populations must be restricted to ensure that waste product levels are reasonable.
Equipment for reef aquaria
Reef tanks are often built up differently than conventional marine tanks due to the specific needs of corals and other invertebrates, and additional equipment may be employed. Protein skimmers, nitrate reductors, ozonizers, and UV sterilizers are more frequent in reef tanks than in fish-only systems, and certain specialized equipment, like calcium reactors, is exclusively found in reef tanks.
Reef tank filtration: The primary goal of filtration for fish-only marine aquariums is the removal of ammonia and nitrite by biological filtration. Natural bacteria convert ammonia to nitrite and nitrite to nitrate, both of which are quite innocuous to fish. (For a more detailed explanation, read our filtering FAQ.) However, nitrate cannot be allowed to accumulate in invertebrates, whereas ammonia and nitrite must still be eliminated. Traditional biological filtration (e.g., canisters) is still employed as the primary filtration in many reef tanks, but the necessity to minimize nitrate buildup has resulted in the development of several reef tank filtration setups. Some of them utilize no traditional filtering at all, while others blend classic and other technologies.
Sumps and trickling filters: Trickle filters were formerly the preferred filtration technology for all marine tanks, both fish-only and reef. While trickling filters are incredibly effective biological filters, the nitrate generated is undesirable. In fact, trickling filters create more nitrate than other filtering systems due to their effectiveness. It is scarcely surprising, however, that there has been a significant shift away from the usage of trickle filters in reef aquariums.
Sumps, on the other hand, are still commonly utilized. Sumps offer many benefits. They may be used to store extra filtration media or equipment. First, they enhance total water volume. Second, they enable equipment such as protein skimming and heating to be placed apart from the main aquarium. However, it should be emphasized that having a sump is not required, and if space or economic constraints make a sump impractical, alternative choices are available.
Nitrate reduction and control: Nitrate is managed in two ways. To begin with, restricting its synthesis, and then eliminating it using natural (biological) or chemical ways in addition to water changes. Nitrate generation is reduced by keeping fish populations low and using protein skimmers.
Protein skimmers remove nitrogenous wastes from the water before they degrade, slowing the generation of nitrate while also removing pollutants and poisons. Their usage is usually considered vital in all but the smallest reef aquarium, and there is no question that they are the single most helpful piece of equipment for reef tanks. There is some evidence, however, that excessive skimming may be harmful to some invertebrates, especially in well-established tanks. This is due to the fact that skimming eliminates suspended food, as well as poisons and trash. As a result, the kind and strength of skimming should be customized to the individual setup (especially in terms of the sorts of coral to be retained), and more food should be provided if required.
Nitrate removal occurs naturally in the seas via two mechanisms: reduction by specific bacteria under low-oxygen circumstances to generate gaseous nitrous oxides or nitrogen gas (which subsequently exit the water through the gas exchange at the surface) and absorption as a nutrient by algae. Both of these processes are applicable in aquaria, with the first, known as de-nitrification, being the more generally utilized.
Denitrators are specialized reactors that promote the development of microorganisms that consume nitrate. A water pump connects them to the tank, and cultures of nitrate-removing bacteria and their diet are introduced. Although formerly popular, these gadgets are no longer widely accessible. They are costly to buy and operate, and it is significantly simpler to promote the development of these bacteria inside the aquarium than in a separate denitrator.
The bacteria that utilize nitrate are often found in aquaria, but the crucial thing to remember is that they will only use nitrate in low-oxygen environments, such as the substrate or deep in cracks and crevices in the rockwork. This is the guiding principle underlying several reef tank designs, notably the Berlin and Jaubert methods. The Berlin technique was the first to use a living rock to induce nitrate breakdown; more current methods use a deep bed of fine marble or sand that also provides regions of low oxygen for nitrate removal. The Jaubert approach is the most advanced of them; a plenum is employed in this system to produce a water area under a deep sand layer.
It is critical to have adequate water flow if live rock and/or sand are used. Almost all corals like turbulent water flow. As a result, powerheads are often employed to offer more circulation.
To create the sand bed, marble “dust” or fine marble gravel may be used in lieu of or mixed with silica sand. This has the added benefit of providing further pH buffering. If a deep sand substrate is not employed, it is preferable to have just enough gravel to support rockwork and burrowing fishes, since a heavy gravel layer may be difficult to maintain cleanliness in a reef.
Nitrate is also eliminated by algae, and algal development may be promoted to assist maintain nitrate levels low. Because too much algae development in the aquarium might choke off corals and other beneficial creatures, this is normally done in a sump. To induce fast development, the algae must be exposed to the bright illumination. This is the biggest disadvantage of this strategy, since purchasing and operating additional lights may be pricey. Furthermore, with the development of excellent hang-on protein skimmers, a sump is no longer required for reef aquariums.
Ozone with ultraviolet light: Ozone is a highly reactive form of oxygen. Ozone generators for aquariums generate ozone using electricity, which is then supplied to the tank through a silicone airline. They are sometimes used in conjunction with an aquarium air pump. The use of ozone in the aquarium is twofold. It is utilized primarily for its capacity to rapidly and efficiently decompose organic matter and other impurities in order to enhance water quality and clarity, and it also kills many water-borne disease-causing agents. When ozone is used, it is frequently introduced into protein skimmers in lieu of or in addition to air. Ozone improves skimming effectiveness in protein skimmers while also offering the advantages listed above. Ozone is usually administered in a separate reaction chamber even when protein skimming is not employed. This is because ozone is hazardous to fish and invertebrates at high concentrations. Toxicology is a frequent concern when utilizing ozone, hence it is generally advised to filter the water with activated carbon before returning it to the aquarium. However, since ozone is very reactive, considerable levels are exceedingly unlikely to persist in the water being returned to the tank, and toxicity is therefore seldom a genuine concern. If you’re still not sure, filtering the water using charcoal won’t harm you. Because ozone causes rubber goods like suction caps and O-rings to deteriorate faster, it is typically advisable to keep the Ozone-reactor or ozonized protein skimmer away or downstream from canister filtration to minimize excessive wear on canister O-rings.
UV sterilizers employ UV-C radiation to kill disease-causing agents, suspended algae, and algal spores. UV light also hastens the decomposition of organic molecules, which helps to enhance water quality. UV sterilization is very efficient in killing disease-causing pathogens like bacteria and parasites, such as marine whitespot. It should be emphasized, however, that employing UV sterilization does not totally reduce the risk of sickness since it cannot destroy organisms that live on the fish. UV sterilization will also destroy useful bacteria and microorganisms; however, it only kills what goes through the device, thus helpful bacterias developed in the tank and filter are unaffected. However, when introducing liquid cultures of beneficial bacteria, UV sterilization should be switched off so that they are not harmed while in suspension. Because UV radiation decomposes certain drugs, it is preferable to switch off UV sterilizers while medicating. Water is fed via a thin quartz sleeve around a UV-C bulb or tube inside the UV sterilizer. These devices may be powered by various forms of filtration (for example, canisters), but they are usually powered by a separate pump. Because the proportion of disease organisms destroyed increases as the flow rate through the unit slows, it is typically suggested to utilize a slow flow rate. A higher flow rate, on the other hand, implies that water is passed through the unit more often, and with each pass, more organisms are destroyed, therefore total efficacy may actually be enhanced. The most significant consideration is to choose a model with enough power for the size of the aquarium. When UV sterilization is used in conjunction with filtration, it should always be on the outflow so that healthy bacteria are not harmed. This also provides clean water to the device, increasing its efficiency.
Calcium reactors: Calcium reactors are specialized pieces of equipment that are almost solely utilized in reef aquariums. Stony corals utilize calcium to construct their skeletons, and if corals are developing successfully in a reef, the available calcium may be depleted. Calcium may be supplemented in a variety of ways, such as using liquid or powder supplements or by using a calcium reactor. In all of these approaches, calcium is provided in the form of carbonates and/or bicarbonates, which helps to maintain carbonate hardness and a steady pH. The calcium reactor has the benefit of always supplying calcium as required, and most reactors may even be connected to a carbon dioxide system with a pH controller to assure pH stability. What is the purpose of a carbon dioxide system? Calcium reactors function by feeding water through an easily dissolvable calcium carbonate matrix (from a canister filter, sump return, or separate pump). Increasing the rate of dissolution with CO2 makes this more effective. However, CO2 is not required in most cases. Even if this is not the case, the steady supply of carbonates will maintain pH more stable than would otherwise be the case.
To summarise, reef tank filtration typically includes biological filtration, protein skimming, and extra circulation pumps. To enhance the growth of nitrate-removing microorganisms, live rock and potentially a deep sand substrate is employed. Ozone and/or UV sterilizers may be used to enhance water quality and eliminate disease-causing contaminants, while calcium reactors give calcium to corals while also helping to buffer pH.
Setting up and maintaining a reef aquarium
Much of the setup for a reef aquarium is the same as for a fish system, therefore almost everything in the preceding section still applies. The biggest distinction is in cycling. Because live rock is almost usually utilized in reef aquariums, it is advisable to start the cycling process with the rock. To begin, normally put a quarter to half of the total quantity of liverock you wish to preserve. Once the ammonia and nitrite levels have peaked and returned to zero, add the remaining rock in one too many batches, monitoring levels and allowing them to stabilize after each batch. Once this procedure is completed, you may go to the next livestock. It is not critical whether you add coral, fish, or other invertebrates next, but you should always add a tiny quantity at a time, preferably hardier fish before the more delicate ones.
Maintenance is similar, but you should pay closer attention to nitrate levels and be prepared to do a water change if they surpass 20mg/l. Small water changes as regularly as feasible are good; for example, you may opt to replace 10% of the water every week rather than 20% every two weeks. A well-built-up reef, on the other hand, should be able to be left for longer if necessary.
In addition to doing water tests in a fish-only marine tank, you may wish to check calcium levels, especially if stony corals are maintained (see the next section for more on types of coral). In hot weather, you’ll also want to keep an eye on the temperature since tropical invertebrates may be injured by temperatures exceeding 28 degrees Fahrenheit, but most fish can survive higher temps (see here).
Depending on the type of invertebrates kept, you may need to supplement with mineral supplements and/or liquid foods on a regular basis.
Positioning corals is a final aspect of reef aquarium setup that is unique to reef aquariums. While most invertebrates (including anemones) may and will move, corals (both hard and soft) remain locked in place. To begin, you should place them according to their requirements. Those that need more light should be put towards the top of the tank, while those who require little or no light may be placed in shady places. Those that collect food need a steady flow of water, while those with delicate structures should not be exposed to direct streams. Avoid putting coral in areas where it will be buried or covered with silt. Furthermore, corals should not be placed too near together since they may sting each other. When crowded, certain soft corals emit substances that might harm other creatures. Other invertebrates, as previously stated, may move, thus attempting to place them where you want them is pointless. Many are not very active but may stroll about until they find a site they like, then remain for weeks on end.