Water Parameters
The ideal water parameters for a healthy reef aquarium are:
Temperature 24-29ºC
Calcium 400-450 mg/L
Salinity/Specific Gravity 35ppt/1.024-1.027
Alkalinity 2.5-3.5 meq/L
pH 8.1-8.4
Ammonia should be undetectable
Nitrite should be undetectable, the acceptable range is 0.0-0.01 ppm
Nitrate should be undetectable, the acceptable range of nitrate for reef tanks is 0.25 ppm, but notmore than 5 ppm
Phosphate should be undetectable,with 0.05 ppm-mg/l being acceptable, and an upper level of 0.1 ppm
Temperature
Maintaining the correct water temperature in your reef aquarium is crucial to maintaining the health of your valuable livestock. The temperature range is ideally kept between 24º-29º Celsius. Temperature can be controlled and maintained by the use of heaters, chillers, evaporative cooling, fans, or by air conditioning the room in which the aquarium is located. Excessive heat can be generated by lighting and water pumps. If possible, allow adequate ventilation below lights and inside hoods. This can be achieved with the use of fans. Try to use external pumps instead of submersibles. All pumps generate heat during operation. External pumps disperse this heat into the surrounding air, rather than into the water. Remember that chillers are a great way of cooling your aquarium, but they also generate heat into the surrounding air. Keep your chiller in a well ventilated position and if possible place it outside or in another room. Do not keep tank lids on while the weather is warm. These prevent evaporative cooling and need to be continuously cleaned in order to allow sufficient light into the aquarium. Corals and invertebrates are sensitive to excessive temperatures. Once the temperature inside your tank approaches 30 º Celsius many corals will experience ill health, some may simply dissolve and die, while others will suffer stress and eventually die if the temperature is not controlled.
Calcium
Normal seawater has a calcium concentration of around 420 mg/L. The ideal concentration in a marine aquarium should be around this number or slightly higher. Stony corals use calcium to build their skeletons. Rapidly growing corals may deplete the level of calcium available within a reef aquarium. Calcium can be replenished in a number of ways. These include liquid or powder supplements, Kalkwasser, or through the use of a calcium reactor.
Salinity/Specific Gravity
Salinity is the measurement of salt in the water and is measured in parts per thousand (ppt). The salinity of seawater in most parts of the world is around 35 ppt. This means that there is around 35 grams of salt in one kilogram of seawater. The easiest way to measure specific gravity is with a floating hydrometer. The more saline the water, the more dense it is and the higher the hydrometer floats. The less saline the water, the less dense the water, and the hydrometer sinks.
Salinity and specific gravity can also be measured with a refractometer. Specific gravity values should be between 1.024 and 1.027.
Alkalinity
Alkalinity is the capacity of the water to resist changes in pH and is also known as the buffering capacity. Normal seawater has an alkalinity of around 2.5 meq/L. Alkalinity in the tank should be maintained at least at this number, and even up to 3.5 meq/L. Alkalinity can be maintained through the use of Kalkwasser, or a calcium carbonate reactor.
pH
pH is a measurement of the acidity or alkalinity of a solution. Excessively low pH makes it harder for calcifying organisms to deposit calcium carbonate skeletons. If pH is too low , the skeletons will begin to dissolve. A pH of 7 is considered to be "neutral", neither acid or alkaline. pH levels above 7 are considered to be alkaline or "base". pH levels below 7 are considered to be acidic.. The pH should ideally be between 8.1 and 8.4. The pH of the water is determined by its alkalinity. If the alkalinity is 2.5 meq/L or above, the pH is will usually be within the ideal range.
Ammmonia
Ammonia is a waste product excreted through the fish's skin & gills or through the build up of fish waste or decaying food. Ammonia is very toxic. It is harmful to fish and invertebrates & will increase stress, lower resistance to disease, damage fish gills & skin, or even result in the death of tank inhabitants. Ammonia is the first compound involved in denitrification and is always present in an aquarium. In a well established tank with healthy biofiltration, ammonia is processed so quickly that is should be undetectable. If organisms within the tank die, or new live rock is added, an ammonia spike may be experienced. Higher tank temperatures and high pH increase the toxicity of ammonia. Ammonia levels may be alleviated by a water changes or through the use of ammonia detoxifying products. Consistently high ammonia levels suggest inadequate filtration. Keep your filters well maintained, avoid excessive feeding, or consider reducing the bioload of your system.
Nitrite
Nitrite is the second step in the nitrogen cycle. Ammonia is utilised by aerobic bacteria ( Nitrosomas spp.) for energy which is oxidised and converted to nitrite. Nitrite can be deadly to your fish and corals even in quantities as small as 1 ppm . It is commonly present during the establishment period of a new tank In a well established tank with healthy biofiltration, nitrite is processed so quickly that is should be undetectable. It is quickly utilised by bacteria which oxidise it to nitrate.
Nitrate
Nitrate is the third stage of the nitrogen cycle. Nitrate is produced as a result of biological action occurring mainly in the aquarium filter system. High levels of nitrate can lead to excessive algae growth & damage plants. Excessive Nitrate is harmful to fish at high levels causing stress, lowering resistance to disease, damaging gills & skin or even resulting in death. Low levels of Nitrate are extremely toxic to invertebrates & corals. In reef aquariums, phosphate levels above 0.5ppm can adversely affect the growth of both hard & soft corals. The easiest way to lower nitrate levels is by performing a water change.
Phosphates
Ina healthy Reef Aquarium the phosphate levels should be maintained at around, with 0.05 ppm-mg/l being acceptable, and an upper level of 0.1 ppm. In saltwater aquariums, a side effect of phosphate is the precipitation of calcium. In marine & freshwater aquariums excessive phosphates can lead to excessive algae growth. These algae can then be eaten by herbivores such as snails. In this way, the snails and other herbivores act as a biological control for excessive phosphates in the aquarium. Phosphates may be found in tap water, or are a bi-product of fish waste or decaying food or algae. Phosphate levels should be regularly monitored in order to limit the levels of phosphate in your aquarium. Phosphates can be controlled with efficient protein skimming. If used correctly, commercially available phosphate sponges are also an excellent method of controlling phosphates. When using absorbing materials or compounds, they need to be changed or rejuvenated regularly. Once they become saturated they they can no longer absorb anything, and what you are trying to remove is just staying in your system.