Aquarium Lighting Options for a Healthy Fish Tank

Clownfish in aquarium

Also see our post about ‘Lighting the aquarium with LEDs‘ here!

The correct aquarium lighting depends on the individual set-up and the light requirements of the tanks inhabitants.

Lighting influences the growth of your aquarium plants, corals, and invertebrates as well as the behavior of your fish. Incorrect lighting will result in many problems, as it is directly related to photosynthesis, CO2, and nutrients.

Appropriate aquarium lighting that meets the requirements of your set-up will enhance the overall appearance and health of your fish tank.

The most common light sources:

  • Incandescent
  • Halogen
  • Fluorescent
  • High Intensity Discharge
  • LED

Before we get started, lets put some definitions in plain English. They are essential for an understanding of the different applications.

The light spectrum describes the combination of colors of which the light consists of. Namely red, yellow, green and blue (rainbow colors).

These spectrums are measured as “color temperature” – Kelvin (K).

Red and yellow produce lower temperatures while blue light produces a higher temperature. Lower and higher defined as the basic sunlight with 5500 K.

The Color Rendering Index (CRI) is indexed on a scale from 0 – 100.

100 being the equivalent to sunlight and how objects would naturally appear. CRI is an expression of the degree to which the illuminated objects appear according to their true natural color.

The intensity of light is given as Lux or lumen. This is very essential, because a light source moved only 2 inches away from the water will be 4 times less intensive. So even if the light source is correct, it might still be insufficient, depending on the distance to the area to be illuminated.

Some General Facts about Aquarium Lighting:

Too much red light could stimulate algae growth in the aquarium. In this case we are talking about 4000 K.

Always select the light in the aquarium according to the natural habitat of your fish. Too much light will not blind or fry them, but they may cause your fish to find places to hide. 

Dust, humidity, water turbidity and dirty vinyl or glass covers will influence the light as well. Intense lighting can lead to increased algae growth. Combined with silicates the result will be brownish algae. Combined with phosphates the result is more red and greenish algae.

You should adjust your aquarium lighting to meet the needs of your set-up and inhabitants. There are always possibilities and creative ways to shade some areas with overhangs.

Incandescent Light (basic light bulb) and the Improvement of the Halogen Light

A CRI of 100 has a heavy red spectrum. The color temperature is 2700 K for incandescent light and 3000 K for halogen light.

This type of lighting should only be used as a supplement for good plant growth due to the increased development of heat.

Fluorescent Light

All fluorescent tubes should be replaced after 6-12 months. Their loss of output over time is significant. This is not visible to the eye however.
Different types are available. Life forms requiring low light will do fine with regular tubes. Corals, polyps, and light intense life forms will prefer HO (high output) or VHO (very high output) tubes.

Full spectrum tubes, come as close to the sunlight as possible. There a combination might be advisable, as corals need a more blue color spectrum.
Of course there are special tubes for plant growth, which work with blue and red spikes (red is especially needed for plant growth) which promote photosynthesis.

Remember that the red color also enhances algae growth.

Halide Lighting

Halide bulbs are more costly but will provide very intense lighting. Best suited for plants and invertebrates.
As a rule of thumb, 3-5 Watt per Gallon of lighting will be the range, but always consider, that light is energy and it really depends on the animals and plants living in the tank.

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Blue light has a higher color temperature, a warmer LED might be an option 2000-3000K for example. Florescent is always an option, especially with fresh water/ no plants.


My son has a high sensitivity to blue light, so no LED , florescent for my 150 gallon aquarium…any suggestions for a great lighting system
Fresh water, no plants
Thank you


Hi I have a 20 gallon tank and a 30” led light bar. I got 8 freshwater fish and all fake plants. How long should I leave the light bar on? And when and what is the blue setting for?

We recommend leaving the light on for 5 hours or less per day for a fish only aquarium. Time your light to be on while you spend time in the room in which your aquarium is. Freshwater fish don’t get a lot of intense lighting in their natural habitat. That means fish-only aquarium lighting is mainly for the benefit of humans. Too much light will only invite excessive algae growth. The blue setting is for ambience only. It can mimic night time / evening lighting.

Larry A

Great read thanks.
I have a 180 community tank with diy LED bulbs. Picked out some cool looking blue Rams at my lfs when I put them in my tank they lost the blue color but it shows back up with my flashlight on my phone. Lol I guess I’m using the wrong bulb? Thanks


Yes that is a possibility, but it could just as well be that the fish are acclimating to the new environment. This can cause stress on the fish and stress can cause the loss of color.

Stephen jay

Okay so I have a black Moore fish just got it . Can I turn the blue led on for a certain amount of time or do you have to leave the main light on all day until you go to bed ? And is it okay to leave the blue light on over night or not ?


Moon light is just for esthetics so there is no issue using it as you see fit. The main light should be on for 6-8 hours if you have fish only, and 8-10 hours if you have plants.

Paul C.

what does the blue led light for? I have a 120cm chihiros led light with all white, I wonder if need I need blue’s for my planted tank.

Blue lights are usually used in reef tanks. Actinic blue lights are often run in combination with with lights during regular lighting hours of the reef tank. Blue LEDs are also used at night by some fish keepers to simulate moon light for a day/night lighting option. For aquarium plants it’s best to just stick with bulbs designed for that specific purpose since they have been developed to provide the ideal light spectrum for healthy growth.


I have a 55 gallon freshwater tank with only about 7 tetras in it. I will be getting a few more fish . I had a 17 watt fluorescent bulb in it that just burned out and I wonder what would be best as a replacement as far as appearance and what’s good for the fish. I don’t want to spend over $50.00. Do you have a recommendation?


The best budget light would be LED’s


Hi, I have a 75 gallon tank I am setting up and I am using two 36″ 18 watt Stunner White LED lights – 8000K each. I had a previous tank where I used these and had a major algae outbreak that I was never able to get under control. I only had the lights on for 8 hours a day. Do you think these lights would cause algae growth? I just don’t want to have the same results with this tank. Thanks!


Light does influence algae growth, together with other factors such as feeding, stocking rate, and general maintenance. Algae outbreaks are fueled by light, but not caused by it. If you keep up with maintenance, feed and stock lightly, the light will be fine.

Joanne Dunkin

I’ve come to the realisation that when I reduce my lighting (ie leaving one of my 2 LED plant grow lights off all day) my Nitrates go up twice as fast. I like the look of the lower intensity of light but the Nitrates go up too fast.

Gwen Letley

I have an aquarium 36″ long – 15″ width – 20″ high, it holds 30 gallons. My husband made a wooden lid, so the light is 2″ above the water line. Up to now I have had Anubias plants and they being doing very well, but I now have brown algae growing on them and the plants don’t look at all well. I did have a few Otto fish, but I’ve lost them and don’t want to replace them. I have now purchased a ballast for a 30″ 25 watt bulb, but really need some help with what bulb I… Read more »


The lighting requirements for anubias are low 1.5 – 2 watts per Gallon anything more will favor algae growth and yellowing leaves. Fluorescent or LED will do fine.


I have a 55 gallon freshwater tank with 2 T8 15W full spectrum bulbs 8,000K. One of the bulbs is burnt and I was thinking of replacing it with a 50/50 bulb with 50% being 6000K sunlight and 50% 03 Actinic Blue light. I have Cichlids in the tank.

Should I be able to expect the same amount of light from the 50/50 bulb as I get from the full spectrum 8,000K bulbs?


No it will not be as bright. The “amount” of light is measured in lumen. Your 15W full spectrum is about 950 Lumen while an actinic is much less. Replacing a full spectrum with a 50/50 actinic the aquarium will have a lesser amount of light.

Arjun Chatterjee

Should I use blue LED for my Fighter fish??

I don’t think it matters, although your Betta may flare when you turn on the light. This would likely be due to his on reflection in the glass caused by the light. If this does happen, try keeping an additional (regular household) light somewhere near the tank and reposition as needed so any potential reflections are either reduced or eliminated.


Could I use a standard led light to light the tank it’s a 90litre I was opting for this because it’s battery powered and could recharge battery’s it will be suspended out from the water wondering will this harm the fish thanks for any advise

Yes you can use LED lights. Just make sure you adjust the lighting period if you notice an increase in algae growth should the LEDs be too intense. Intensity of LEDs varies however so you’ll have to gauge this yourself. If you are lighting a reef tank then you should be sure you are using the right light spectrum and intensity to meet the reefs requirements. For freshwater, most standard LEDs should work just fine.

Franky Day

my fish tank looks cloudy I have slimline 36″ fluorescent tube 30 watt about 2 inches above the water under a wooden top, how can I get water get the water to look clear so I can see my fish clearly?

Thilo @ Algone

Light can be a contributing factor, but is likely not the cause of cloudy water. The most common factors in established aquariums are overfeeding and or overstocking. In addition, chemical/ biological imbalances through changes in the setup. There are some variances between marine, reef, fresh and planted aquariums, but the previous is the common ground.

Evaluating the maintenance routine should be followed by the appropriate steps in regards of the type of cloudiness. Whitish (bacteria bloom) or greenish (algae bloom). Please consider the articles on our site on cloudy water. There you will also find more specific remedies on the issue.


I replaced my “aquarium” fluorescent light with a “standard” fluorescent light. Now my fish seems sick with some ick. Could switching the light bulbs have caused them stress thus making them sick?

Scott @ Algone

Joe the light has no affect on ich in any way, shape or form. Ick is a parasite. You do need to start treatment immediately. Please use this link to learn more


Will a red light bulb change the water clarity, meaning will the water become more clearer or dirtier?

Thilo @ Algone

Yes and no. Light in the red spectrum is beneficial for the plants (including algae). If you have high nutrients, such as nitrates, intensifying light can cause algae to bloom and the water to appear murky. It can also have the opposite effect, because if the plants can increase growth due to proper light, the nutrient uptake by plants will be more efficient. This can make water clearer.

Scott @ Algone

Fluorescent lights are still a great option and it’s hard to beat their low cost for sure. And I also agree that halides truly rock the reef, but the draw backs are high heat and high power consumption. LEDs are definitely a great new option any serious reef keeper should consider. They run cool and are super efficient!

aquarium setup

I prefer florescent lights over the other options. The cost is pretty low these days and you can mix and match tubes to get just the right look. Getting enough light into deep tanks is the only drawback, for which halides work well- I just don’t like how insanely hot they get! 😀

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