Calcium

 

Calcium is one of the most important levels to keep an eye on while maintaining a custom reef aquarium. Most corals use calcium from the surrounding sea water to form their skeletons which is composed primarily of calcium carbonate. Studies have shown that as the calcium level drops below 360 ppm in a reef aquarium, it becomes increasingly harder for corals to collect ample calcium for calcification (i.e., skeletal growth). That is why it is recommended that most aquarists keep their calcium levels around that of which you would find in natural seawater (~420 ppm). Studies have shown that bringing calcium levels above 420 ppm does not improve calcification. Which is why maintaining a calcium level in your tank close to that of natural seawater is recommended (anywhere between 380 and 450 ppm)

 

Alkalinity

 

Next of the list of important water parameters is alkalinity. Alkalinity (bicarbonate) works covalently with calcium in the calcification process and is just as a necessity to monitor as calcium in a successful reef aquarium. Corals use up bicarbonate in the surrounding sea water and turn it into carbonate and use that along with calcium to build their calcium carbonate skeletons. However testing bicarbonate is easier said than done and most situations testing bicarbonate is inaccurate or impractical. As a surrogate for testing bicarbonate reef aquarists test for alkalinity since bicarbonate generally reads the same ions that contribute to alkalinity. Alkalinity measurement is simply the amount of acid (H+) needed to bring the pH down to 4.5 in the aquarium water.

 

 

 

 

Salinity

 

This one seems like a no brainier however not monitoring regularly monitoring the salinity level of an aquarium can lead to coral bleaching and other unnecessary fish deaths.

 

Cells in marine organisms have internal regulatory system that expand and contract depending on the salinity levels of the tank. This is known as osmoregulation.

 

Osmoregulation is the active regulation of the osmotic pressure of an organism's fluids to maintain the homeostasis of the organism's water content; that is it keeps the organism's fluids from becoming too diluted or too concentrated.

 

Basically what that means is that if the cells become too diluted with salt they will dry up and die and subsequently if they become too concentrated with fresh water (i.e. low salinity readings) the cells will rupture.

 

Natural ocean water has a salinity of about 35 ppt, corresponding to a specific gravity of about 1.0264 and a conductivity of 53 mS/cm so I would say shooting for any other salinity level different than natural seawater would be at the aquarist’s discretion.

 

Temperature

 

79° F year-round is a good level to keep a marine aquarium at. It is recommended to keep your tank a little cooler in the summertime. As temperature rises, Co2 and O2 are less permeable in water. This is why it is recommended not to let your tank run too hot and inhibit calcification due to inadequate O2 levels. A chiller is usually necessary on systems running lots of metal halide lights and/or pumps that warm up the aquarium water as they run.

 

All things considered, temperatures in the range of 77-81° F will suffice unless there is a habitat specific reason to keep the tank beyond that rage.

 

 

PH

 

The Ph of natural seawater varies greatly depending on location and even depth. However for the custom reef aquarium about 8.2 is appropriate. Some reefs and habitats can obviously thrive in a much wider Ph range.

 

 

The Ph range from 7.8 to 8.5 is generally appropriate for the reef aquaria, with a couple guidelines:

 

A.) If you choose to run a reef in a low ph range in mind, (such as a pacific style reef) make sure to maintain a calcium level of at least 400 ppm. Sometimes when Ph and Calcium levels fall, (which is not uncommon in a tank with Co2 injection) calcification can be stunted if the calcium is not at an adequate level

 

B.) Coral calcification can be quickly stunted in situations where ph reaches the low or high extremes, however aquariums can still operate successfully in the low 7.8-7.6 range if you make sure alkalinity and Calcium are adequate. Tanks with Co2 injectors are able to successfully keep a stable reef aquarium at lower Ph readings due to the fact that Co2 keeps the carbonate alkalinity in the water reasonably high.

 

C.) On the opposite side of the spectrum, Calcium carbonate precipitates abiotically when the ph is higher than 8.5 causing a drop in calcium and alkalinity, and subsequently clogging heaters and pump impellers with calcium deposits. Make sure to keep calcium and alkalinity at a comfortable range if you choose to run an aquarium that sometimes reaches 8.4 or higher, which is not too uncommon when dosing limewater.

 

Magnesium

 

Magnesium in an important element to maintain in the reef aquaria as its collaboration with the calcium and alkalinity balance is a crucial one. Magnesium binds to calcium carbonate crystals which keep them from attracting more calcium and carbonate and growing into deposits. One should try to maintain the natural seawater level of magnesium. Higher or lower levels can cause problems.

 

 250-1350 ppm is fine, and levels somewhat outside that range (1200-1400 ppm) are also occasionally suitable. It is recommended that magnesium levels should be measured after every water change to ensure they are adequate. If the aquarist is having trouble maintaining stable calcium or alkalinity levels in their aquarium, or they are experiencing a large amount of abiotic precipitation of calcium carbonate on their pumps and equipment, chances are low magnesium levels are the culprit. 

 

Phosphate

 

Many macro algae, corals or other rapidly growing organisms in the reef aquarium readily consume phosphate. Phosphate that does not get consumed by typical reef inhabitants at the rate of which calcium or even ammonia does which is why it is recommended to keep phosphate below 0.03 ppm. When phosphate rises above natural levels it can- A.) Stunt the calcification process causing corals not to grow and B.) Trigger unwanted algae blooms in  the aquarium. That being said it is important to not let you phosphate get to levels above 0.03 ppm.

 

Ammonia

 

Ammonia is necessary element to keep an eye on in the reef aquarium, although toxic to most marine inhabitants, it does have benefits in the marine tank at lower concentrations, some macro algae species willingly consume it to make proteins, DNA and other nitrogen containing biochemicals. Bacteria also consume ammonia and turn it into nitrite, nitrate, and then nitrogen gas (the nitrogen cycle). In an established reef aquarium ammonia is rapidly consumed and turned into nitrogen before it becomes harmful to fish. However it is still recommended to test your ammonia levels periodically to make sure everything is running smoothly, particularly after a water change.