Water Chemistry I

When simulating any environment, the conditions in which the animals live is of the upmost importance. Many of the different seas and oceans from which fish and invertebrates hail from have different water conditions. Even the Atlantic and Pacific Oceans even have different parameters. Now in the home aquarium there are general levels which are widely accepted and provide for the best possible habitat for all the animals.

Temperature
More often than not, the home aquarium will run cold instead of hot; with the temperature drifting towards room temperature. This can easily be rectified by the use of a heater which should be set between 76º-80º. In the event that the aquarium runs warmer (ie: greater than 83º) a chiller may be needed.

pH
Chemically, the pH of a system is the measurement of the concentration of the Hydrogen (H⁺) ions in the system in ratio to the Hydroxide (NH^-) ions. In context, the pH is a measure of the acidity of a system. Whereas a pH value of 7 is neutral, anything higher means the system is basic or alkaline, and anything lower than 7 means the system is acidic. In saltwater the pH should be maintained between the values of 8 and 8.6. These values can be easily reached using one of the many pH buffers available in the hobby.

Specific Gravity
The concentration of salt in the aquarium is quantified using a measurement called specific gravity. On average, the specific gravity of the ocean is 1.025 – so this is the value we try to establish and maintain in a reef aquarium. A fish only system can have a greater variance with a target value of 1.019. The lower specific gravity is recommended for a fish only aquarium because, while the fish will still thrive in less dense water, parasites and pathogens will not.

Ammonia
Ammonia (NH₄⁺) is highly toxic. It is introduced in the system through fish waste and the decomposition of organic materials such as food in the aquarium. In a healthy system ammonia should be broken down into less toxic nitrite rapidly by the beneficial bacteria housed in the biological filtration. As such, ammonia should always read at 0 in a healthy aquarium since it is extremely detrimental to the health of all the inhabitants.

Nitrite
The first by product of the consumption of ammonia by bacteria is nitrite (NO₂^-). While less toxic than ammonia, it still poses a large risk to aquarium inhabitants as it can prevent the absorption of oxygen by fish. Thus nitrite as well should always read 0 on a chemical test. Despite this fear, in a healthy aquarium nitrite is also broken down into the less toxic nitrogenous compound nitrate.

Nitrate
Being the final step in the nitrogen cycle, nitrate (NO₃^-) is the least harmful. It should be maintained at concentrations of less than 12.5mg/l in a reef tank and 25mg/l in a fish only tank. Nitrate is not removed, nor broken down in any significant amount, (however a few special animals such as xenia and caulerpa will absorb small amounts as food), thus the only way to remove nitrate, which is toxic in concentrations above the before mentioned values, is through water changes.

Phosphate
Phosphates (PO₄^3-) are produced in the aquarium much in the same way as nitrates are (ie fish waste, uneaten food, ect) and have similar side effects. While not as dangerous as ammonia, phosphates in low concentrations (0.1+) can effect corals, and in higher concentrations (0.5+) can have adverse effects on fish. Phosphate also serves as being one of the principle structural building blocks for algae. For this reason, if you are having a large algae bloom, or algae is growing uncontrollably - check your phosphates! They can be easily removed using one of the many commercially available phosphate absorbent medias.

Water Chemistry II

In the case of a reef aquarium, there are additional elements that need to be monitored and maintained in order to provide the proper conditions so the corals and invertebrates will live with longevity and reproduce.

KH
Alkalinity or KH is a measure of the total carbonates (CO₃^2-) and bicarbonate (HCO₃^-) in the water, KH serves as a buffering agent for pH in the water. Carbonate and bicarbonate serve as a safeguard for a sudden drop in pH. These two molecules will remove excess free hydrogen atoms in the aquarium which are the cause for a lower pH.

Calcium
One of the most important molecules in the aquarium, calcium (Ca²⁺) serves as the primary building block for the structural development of both fish bones and coral skeletons.

Magnesium
Magnesium (Mg²⁺) acts similarly to calcium in the aquarium and serves a similar role. While it is also structural, magnesium provides a buffering capacity for the maintenance of calcium levels in the aquarium. Magnesium is more readily bound into molecules than calcium, so it will often substitute for calcium atoms in molecules thus freeing up the calcium for use by the animals in the aquarium.

Strontium
Another structural molecule, Strontium (Sr²⁺) is also used by corals for skeletal development.

Iodine
Iodine (I^-) is a very important chemical. It is utilized by all corals and plays a key role in tissue growth. For the rapid growth of soft corals, adding iodine is key. However, iodine can be very hazardous if overdosed!

Iron
Somewhat of a minor chemical, iron (Fe²⁺ and Fe³⁺) is very important if you plan on having a refugium. Iron is crucial for the growth of saltwater microalgae’s such as caulerpa or chaetomorpha. In addition supplementing the reef aquarium with iron can speed up the growth of the decorative purple coralline algae.