On average, most tropical aquariums do best with temperatures ranging from 23 to 28 degrees Celsius (73-82 degrees Fahrenheit).

The type of lighting depends upon what kind of animals you desire to keep. One of the most important factors is the light intensity. A high color temperature is also important. Aquarium lights with color temperatures ranging between 5,000 to 7,000 degrees Kelvin would give excellent colors to a marine system. Another factor is the "Color Rendering Index" or CRI. The CRI of sunlight is 100 and a high CRI on an artificial light means that it is very close to replicating the colors of natural sunlight.

Salinity is a measure of the total amount of dissolved salts in seawater. It is measured in parts per thousand (ppt or 0/00). The average salinity of the ocean is around 34 to 37 ppt. Marine aquariums are also measured in specific gravity. Specific gravity may be defined as the ratio of the density of the liquid to the density of water. Since density of liquid varies with temperature, so does specific gravity. It has been determined that liquids with a specific gravity less than 1 are lighter than water; those greater than 1 are heavier than water. The specific gravity of seawater at 35 ppt is 1.026. The proper range for a marine aquarium is 1.020 to 1.026. Refractometers and hydrometers can be used to estimate salinity in marine systems. Many different kits are available at local aquarium shops

pH is an abbreviation for pondus hydrogenii which also stands for "Power of Hydrogen" or "Weight of Hydrogen." pH is a measure of the effective acidity or alkalinity of a solution. It is expressed as the negative logarithm of the hydrogen-ion concentration. Pure water has a hydrogen ion concentration equal to 10-7 moles per liter at standard conditions. The negative logarithm of this quantity is 7. Pure water has a pH value of 7. The pH scale usually is considered as extending from 0 to 14. As the scale drops towards 0, the solution becomes more acidic. As the scale rises toward 14, the solution becomes more basic. Small pH testing kits are available at most aquarium shops. These kits have color codes to indicate the approximate pH.

Three Types of Filtration:

There are three major types of filtration used in marine aquariums -- mechanical, chemical and biological. A good mixture utilizing all three types of filtration would be advisable Biological filtration utilizes bacteria to break down waste material in the water. During mechanical filtration, small particles in the water pass through the filter media and get caught. Example of this would be rapid sand filters in large aquariums and simple foam pads in home aquariums. Chemical filters may utilize activated carbon to remove dissolved molecules from the water. Another example of a chemical filter would be a protein foam skimmer. All types of filtration are readily available in most aquarium shops.

Undergravel Filtration:

Undergravel filtration is a simple way to filter the aquarium. It is usually made of a flat plate or screen which is set up off the aquarium bottom, leaving a small empty space below it. Filter media (usually gravel) is placed on top of the filter. there are at least two uplift tubes which are connected to the space below the filter and draw water up through them as a result of an air pump on the top of the tube. In this situation, the water passes down through the gravel and then back up to the surface of the aquarium through the uplift tubes.

The most colorful fish are found in marine habitats. A marine or saltwater aquarium is desired by many aquarists. A marine aquarium is more difficult to maintain than a freshwater aquarium. Salt, being a corrosive agent, can be damaging to a lot of aquarium equipment. Constant monitoring of the cleanliness of the aquarium, inside and out, is important to the overall appearance of the area. A freshwater system, on the other hand, is much easier to maintain. A weekly cleaning will usually suffice to keep the appearance looking good. There are many freshwater fish that are just as colorful as marine fish and will do very well in a home aquarium. When setting up an aquarium for the first time, a freshwater aquarium is suggested.