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Lighting Your Tank
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What type of lights to use?

I usually see many people ask about lighting options on fish boards or ask how to fix the problems they are having (this goes back to planning when setting up a new tank). It is easy to get confused about lighting as there are so many options and often misguiding info from manufaturers on what is best for your tank.

I will try to cover the basics of aquarium lighting in this article, what you ultimately choose will depend on two factors, the type of aquarium your are creating and the amount of money you have available, as lighting is most often the most expensive part of any tank.

Most aquariums are sold with standard fluorescent or incandescent lighting that is seriously under powered or poorly suitable for decent viewing and is absolutely unsuited for any live plants. Deciding on the proper type of lighting is key to the success of your tank. Be sure to check the lumen, and light spectrum requirements of the fish or plants to be kept before buying any lighting products. Once you have decided what will be in the tank, you can determine the lighting requirements of the aquarium.

Cost is always a factor, but especially when one is looking into a high-light setup for a planted aquarium. Metal halide, compact fluorescent, or combination lighting systems can often cost more than the tank, filters, decorations and fish combined. Make sure the lights are not only affordable now, but also in the future as bulbs will wear out, and need to be replaced. Check to see what the cost is of replacement bulbs, most aquarium bulbs need to be changed about every 6 months to once a year to be effective.

A word about bulb spectrum and CRI. Different colors are perceived by varying wavelengths of the light emitted. This frequency is usually given in nanometers (1 nm = 1/1,000,000,000 of a meter). Red is a low frequency, long wavelength light. The faster the frequency from that point shows colors through orange, yellow, green, blue, indigo, and finally violet (and into ultra-violet or UV), which has a higher frequency and shorter wavelength. Often, bulbs are given a Color Rendering Index or CRI. This is a scale from 1 to 100 of bulb's ability to accurately render all colors in the visible spectrum. The 'whiter' the light, the higher this number will be. Some aquarium bulbs (or tubes) have peaks in their spectra to emphasize colors or boost light output in the ranges needed for photosynthesis. This will tend to distort the natural colors present and yield a lower CRI. Full spectrum bulbs provide close to the same intensity of light in all frequencies in and therefore offer a higher CRI.

Aside from plants that have different lighting needs, make sure you keep your fish in mind when purchasing aquarium lighting. Some common aquarium inhabitants can easily be stressed and/or killed as a result of incorrect lighting decisions. Long-term stress and/or death may occur from slight misjudgments in certain aquarium applications. Next I'll discuss some of the different types of lighting available.

Incandescent Lighting has been a popular form of aquarium lighting for many years. It is an inexpensive light source that is often found in small aquarium hoods. This lighting offers many colors, and bulb strengths. One important note is that incandescent lights produce a significant amount of heat. Smaller aquariums (which is where you usually find these bulbs) are especially vulnerable to temperature changes caused by the heat from these bulbs.

Aside from the heat, the spectrum of the bulb is not consistent, bulb life is short, and they are inefficient at high lumen output in deeper tanks. Incandescent bulbs are not at all recommended for planted tanks.

Because of the heat produced by this bulb, proper circulation and/or ventilation is essential. An efficient heater is also mandatory in most applications because of the temperature changes, that can take place when the light turns off.

Fluorescent lighting is probably the best all-around bulb for most tanks as they can cover almost any application needs and are readily available.

Flourescent bulbs are basically long glass tubes which contain phosphor bits, and when an electrical current is run through the tube, these phosphors heat up and emit visible light. Different mixes of phosphors will give different properties of spectrum and intensity, resulting in different light colors.

Fluorescent bulbs for aquariums come in three main forms. These are normal output (NO), high output (HO), and very high output (VHO). The bulbs come in many different colors and wattages, and most bulbs run very cool, are inexpensive, and have a relatively long bulb life. They are also available in many bulbs lengths, covering most standard tank sizes.

Fixtures for these bulbs come in many shapes and sizes and can be found through most hardware stores or specialized fish stores. Most aquarium are sold as a tank/top/light combination that contains a flourescent fixture, these lights are usually acceptable to fish viewing and nothing more. Planted tanks require up to 2 watts per gallon of light to be considered a low-light tank, more often than not these light fixtures have less than half a watt per gallon.

Each bulb requires a ballast, which transforms energy from the electrical outlet to the bulb. Many fluorescent lighting hoods now offer electronic ballasts that can be operated by timers for automated lighting control. It is even possible to "overdrive" flourescents with an electronic ballast, but that is an advanced project I will cover seperately

Freshwater plant tanks almost always use multiple fluorescent bulbs to create the correct lighting for optimum plant growth. Mixing fluorescent bulbs with other lighting types (ie. metal halide, compact) will offer increase in overall lighting lumens, and color rendition of the total lighting system. Advanced hobbyists are known to mix bulbs and color temps to certain effects.

For most aquarists who intend on keeping tropical fish only or a low to medium light planted tank, this is the most cost effective lighting available.

Compact lighting is quickly becoming a standard, especially with planted tank owners. These powerful and energy-efficient lights are available at some fish stores or online outlets, and offer the best long-term economic value for high intensity lighting needs.

Compact fluorescent technology offers several advantages over conventional fluorescent lighting:

They provide considerably more light output, which in turn gives you a brighter tank.

They are smaller in size than the fluorescent tubes, and can put out much more light. The bulb life is long, longer bulb life saves money and time.

They consume less electricity than conventional fluorescent lighting, which makes them very efficient and economical.


Most compact fixtures are sold as a complete aquarium hood. Many of which are very attractive and include features like cooling fans and moonlights. However, retro-fit type systems, and do-it-yourself kits are also currently available if you wish to upgrade your current light fixture. Most power compact ballasts are timer-ready, and easily enclosed in a hood area, or underneath the aquarium. These are small and energy efficient.
Compact bulbs are also known for their depth penetration. With every inch of aquarium water that light has to penetrate, significant intensity is diminished, most conventional fluorescent bulbs are dramatically effected by this.
For high lumen, and full spectrum lighting needs, some people mix and match the compact lights with metal halide, or fluorescent bulbs. The effects of this combination on saltwater reef aquariums is especially notable. Most bulbs are sold from 28 to 96 watts per bulb, and offer many color renditions. Screw-in compact flourescent bulbs are also available as an effective replacement to incandescent bulbs for smaller tanks and are available in 10 to 20 watt bulbs in different color spectrums.

Metal halide lighting offers a beautiful and intensive lighting source that produces a "sun like" effect on the water, and will create a dancing, rippling reflection of light in the tank unmatched by any other current aquarium lighting. Metal halide lights are very popular with reef tank and advanced high-light planted freshwater tank owners.

There are many options to consider when metal halide lighting will be purchased. Keeping in mind what will be kept in the aquarium first, you then need to decide how bright the bulb should be, and what color light you desire from the bulb. The other issue is cost as metal halide lighting is the most expensive of all the lighting options we have covered.

Metal halide bulbs are sold in common wattages of 50, 150,175, 250, and 400 watts. There are also a variety of temperatures to choose from. The common choices 4500, 5500, 6500, 10,000, 12,000, 15,000 and 20,000K bulbs. The K represents degrees Kelvin. The lower the degree K, the whiter or more yellow the lamp appears, the higher, the more blue the lighting appears. Many freshwater plant enthusiasts prefer a lower Kelvin bulb (around the 5500-6500 K range) for freshwater plants. Saltwater reef hobbyists use bulbs in the more blue range (10,000-20,000 K range).

Metal halide lighting also puts out heat and will raise the temperature of the aquarium water. Tank overheating is a serious and othen occuring problem, some tanks will need a chiller to cool the water, especially tanks that contain fish with strict temperature parameters.

The lights come in many different forms as well, some include, pendants, independent bulb hoods, ventilated hoods, combination (fluorescent, compact, halide) hoods, hi-tech hoods, retro kits, and other do-it-yourself type kits.

A ballast is required to run your lights. The ballasts convert the electrical energy into bulb energy. Some systems come with their own ballast, some require the separate purchase. Electronic ballasts are the most efficient, and versatile. However they are more expensive than the former tar style ballasts.

Something worth mentioning is that general purpose Halogen lights are unsuitable for aquarium use. They are typically offered as low-cost work lights and in the tochiere and track lighting. Although offering a high lumen light source, the spectrum is not suitable for most applications, such as live plant or reef tanks. So cheap DIY applications using these fixtures is not recommended.

No matter what what lighting option you use, make sure you research the fish and plants that will be in your tank. There is nothing worse than finding the plant you always wanted and then watching it melt away because the light was not strong enough to sustain it. Lighting is truly one of the most important choices to make for any fish tank, even one without plants or corals, don't cut corners when it comes to lighting your tank. A word of caution about natural sunlight, DON'T DO IT! While the sun is perfect for plants and fish in their natural suroundings, a tank made of glass or acrylic isn't a natural surounding! Sunlight through windows can lead to algae blooms, temperature swings and other disasters.

With the correct lighting, your tank will be an inviting focal point of any room for you and a great home for your fish.

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All the postings and articles are the property of Ecotanks Fish Blog and are written by Bill Carpenter unless otherwise noted. No use of these posts or articles without the express written permission from Bill Carpenter is allowed.