Light spectrum and intensity in nature
There are a number of factors that affect the color and intensity of light in aquatic environments in nature. These factors include the depth and clarity of water, weather, and clarity of air. Because of these factors, and the fact that water conditions vary between habitats, the spectrum and intensity of light will vary from one aquatic environment to another.
Light spectrum and intensity for aquariums
Fish-only aquariums
The function of the lighting system on a fish-only aquarium is to provide the fish with a simulated day and night cycle that is necessary for their overall health. Because the spectrum and intensity of the light are not as important as they are for an aquarium with plants or corals, the lighting system for this type of aquarium can be designed based upon other factors involving cost and aesthetics. When determining the cost of a lighting system, take into account not only the initial cost, but also the operating cost of the system. When budgeting, choose a lighting fixture that does not consume excessive amounts of electricity or the need for frequent bulb changes. A good rule of thumb for a fish-only aquarium is to allow 1 to 2 watts per gallon of water. A good choice for this type of setup would be either a standard or a power compact fluorescent system. The spectrum of bulb chosen for this type of setup will only be determined by personal preferences. Generally, a lamp that is focused more on the red part of the spectrum (low K rating) will exhibit colors better than a lamp with a higher Kelvin rating. But, lamps with a low Kelvin rating tend to grow algae at a much faster rate, resulting in more maintenance. If your goal is to illuminate the aquarium with a color-enhancing bulb, you can avoid the excessive algae growth by either using a liquid algae destroyer, or by decreasing the number of hours in a day that the lights are on.
Freshwater planted aquariums
There are a few considerations that need to be made when deciding what type of lighting to install on a freshwater planted aquarium. These considerations are; intensity and spectrum of light, initial and operating costs, and the heat generated by the lighting system.
Most of the freshwater aquatic plants that are available on the market originally came from the shallow tributaries and rivers of Central and South America. The water clarity in these areas is typically murky to stained. Because of the shallow waters that these plants come from, the spectrum of light that they are subjected to is going to be in the full spectrum range, similar to natural daylight. This range on the Kelvin scale is between 5500 K to 7500 K. The intensity of light that the various plants require is going to vary due to the contrasting water qualities in that part of the world. A general guideline to follow when customizing a system is to provide between 2 and 5 watts per gallon depending on the species of plant to be kept.
The initial and operating costs vary widely among the different types of lighting, as well as the type of ballast used with that lighting system. Again, it is often a better idea to buy the system that may be more expensive in the beginning, but is less expensive in electricity usage and bulb replacement. Also, when considering a particular lighting system, make sure that bulbs are available for that system in the proper spectrum range. Some lighting systems are targeted specifically towards saltwater reef aquariums and full spectrum bulbs may not be available.
Last, the heat generated by most of the more powerful lighting systems is considerable, and has to be addressed in the installation of the system. Cooling fans and possibly a water chiller may be needed to maintain the aquarium at the proper temperature. Room temperature also plays a big role in aquarium temperature and needs to be addressed along with the heat developed by the lighting.
Once you have decided on a lighting system, you can then research the different types of plants that are available. Base your decisions on the type of plants that you wish to incorporate into the system by the amount of light that you can provide for those plants.
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