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Q10468 - INFO: Lighting: What To Know Before You Buy by a Marine Depot Staff Member

Before you purchase a light fixture for your aquarium there are a few items you should know.  By understanding these items it will help you make a more educated and appropriate choice for lighting your aquarium.


  1. Understanding the different types of lights/bulbs available:
    The most popular and common types of fixtures available to light your aquarium include Normal Output fluorescent (NO), Very High Output fluorescent (VHO), Power Compact fluorescent (PC), T5 High Output (T5HO) fluorescent and Metal Halide (MH) light fixtures.  The brightest of these fixtures are the Metal Halide fixtures and the least bright are the NO florescent fixtures.
  2. Matching the right light to your aquarium:
    For a fish only aquarium you can use any type of lighting you wish to.  The most popular type of lights for a fish only system is the NO fluorescent fixtures.  They generally will be the least expensive and will provide enough light for viewing your fish.  If you are going to be keeping live plants or live corals in the tank you will need a lighting system that will provide plenty of light for the plants and symbiotic algae found in corals to photosynthesize.  This can be accomplished using multiple NO output bulbs over the tank or high output lights such as a VHO, PC or T5 fluorescent fixture or a MH system.
  3. Spectrum of the bulbs:
    Bulb will be available in different spectrums or colors.  The spectrum ratings are listed by a Kelvin (K) temperature scale.  The lower end of the K range bulbs you will normally see are 5500K-6700K bulbs.  These bulbs will generally be a greenish (5500K) to a yellow color (6700K) in color and are a good spectrum for growing live plants.  The next most common color seen will be the 10000K bulbs.  These are generally a crisp white color and while not as good for your plants they will still provide beneficial light without the yellow look.  As you go higher in K rating (12000K-20000K) the light will start taking on a more bluish hue.  Generally the higher K bulbs are used in saltwater setups.  Most of your NO bulbs will simply be labeled “color enhancing” or “plant grow” bulbs for an easier selection.  For a fish only system, the color enhancing bulbs are generally your best choice.
  4. How much light is needed?
    For a fish only system there is no real rule of thumb to go by.  The light is mainly there for you to be able to view your fish.  As long as the bulb(s) extend the full length of your aquarium you should be fine.  For planted aquariums the wattage of light needed will depend on the type of fixture used and the depth of the tank.  For lower output lights like NO fluorescents a good starting point would be about 2-5 watts per gallon of water.  Higher output lights like VHO, PC and T5HO should be good with around 1-3 watts per gallon of water.  For metal halide fixtures you will need one bulb for every two feet of tank length and the wattage will depend on the depth of the aquarium.  A general guide line would be for tanks under 22” deep go with 175 watt bulbs, tanks 22-28” deep use 250 watt bulbs and for tanks over 28” tall use 400 watt bulbs.
  5. How long should your lights be kept on?
    For a fish only system you can keep your lights on for as long as you wish with the average time being around 4-8 hours per day.  If you are having issues with severe algae growth in the aquarium you can lower the amount of time the light is on to help inhibit the algae growth.  For live plants the lights should be run from 10-14 hours per day to allow the plants plenty of time to photosynthesize.
  6. Use timers for a more stable environment in your aquarium.
    Fish are very much creatures of habit.  They enjoy things staying fairly stable including the lighting schedule.  By putting your lights on timers to come on and off the same time every day the fish will generally be less stressed and overall healthier.
  7. When considering the price of a lighting fixture, you should also look at the replacement costs of the bulbs.
    You should not wait for your bulbs to burn out before replacing them.  Bulbs will slowly dim over time and many times this is not noticeable to the human eye.  The lights over a planted aquarium should be replaced every 8-12 months and for a fish only system the bulbs should be changed every 1 to 2 years.
  8. You will need to consider how to mount the lights over your aquarium.
    There are two different types of fixtures available, fully assembled and retrofit kits.  A fully assembled fixture is basically ready to go right out of the box.  Most will come with mounting legs or hanging kits.  Mounting legs will allow you to set the fixture right on the rim of your aquarium while the hanging kit will allow you to suspend the light over your tank.  If you have a canopy over your aquarium usually a retrofit kit is your best option.  It will mount right inside the canopy with a few screws.
  9. So you want to light a reef tank?
    What is the ideal lighting for a reef tank?  While this is a highly debated topic from the type of light (metal halide vs. VHO vs. PC vs. T5) to the spectrum of the bulbs you must figure out what works best for your tank and the type of corals you plan on keeping.  If you are mainly going to be keeping soft corals (like leathers, mushrooms and xenia) you probably don’t have to invest in a metal halide system for your corals.  If you are keeping SPS corals (such as Acropora and/or Montipora), clams and anemones you will want to give them as much light as possible.  Research the lighting requirements of the photosynthetic organisms you want to keep in your tank and find a lighting system that suits their needs.  If you are not sure what type of corals you want to keep it is probably better to go with a higher wattage fixture to be on the safe side.
  10. What is your lighting system going to cost you (on your electric bill).
    Since everyone has different electric rates in different parts of the country (and world) it is hard to give an exact estimate of how much running a given fixture will cost.  To help get a rough estimate you can take the wattage of the fixture (add up the wattage of the different bulbs) and using your electric rate you can get an approximation.  There is a factor to consider also and that is the type of ballasts used.  Electronic ballasts such as IceCap ballasts can help reduce the electrical consumption of a lighting system.  For example their fluorescent ballasts will use about 30% less electricity compared to conventional fluorescent ballast.  Also don’t forget that your lighting system will not be running 24/7 like other items on your reef tank.  Running the lights for 8-12 hours per day in most cases will be perfect.  Just for an example if your electric rates are $0.11 KWH and you are running a system with 500 total watts for 10 hours per day it will cost you about $15 per month to run that system.
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Approved Comments...
This article is excellent! Let me ask about what kind of light I need? I have a 29G planted tank, with an Aqueon Colormax T5 (6700 daylight 18 watt; Colormax 18 watt) My plants: alternanthera reineckii cardinalis, lobelia cardinalis, cryptocoryne wendtii, staurogyne repens, baby tears, dwarf hairgrass and red and green cabombas. Its good or I need more light? Thanks for your answer :) Approved: 6/23/2014
Need info on LEDs. But other info was good. Thanks! Approved: 10/21/2013
Excellent but I too would like more info on LED and also the need for use of a chiller Or at least a reference and link. Not being critical just needing advise badlt. What is here is excellent! Approved: 7/7/2013
LED??????? Approved: 4/6/2013
It is definitely goog information, but like many of the more recent posts- I would appreciate LED information added into the mix. Since the article hasnt yet been updated to reflect the current (and growing) trend to utilize LEDS for all purpose lighting- it should be rewritten to include this information. Additionally, I would appreciate more discussion on the differences in lighting intensity and heat output, and how many bulbs in a setup. A former aquarist at our facility had invested in MH lighting that was too large for our tank systems systems- and that also required both actinic (blue) and white lighting. Not only was the growth in the tanks obnoxious (mainly fish only, with some live seaweeds)- but we actually ended up with a fire and the MH fixture itself was melted in the process. Obvously not a good choice. All MG lighting has been removed from the facility was replaced with flourescents. We want to move to LED ligthing and away from our more common flourescent lighting to o Approved: 3/18/2013
I would like some LED discussion! Approved: 2/4/2013
Gives a good general description on lighting, however, it is a very complicated science and it seems everyone has an opinion. Where I get a bit overwhelmed is in the mixing of different spectrums of light and what concentrations of each I should use. Approved: 1/30/2013
great refresher information Approved: 12/25/2012
No discussion of LED lights or the possible need for a chiller with other lights. Approved: 12/22/2012
Gives adequate information in easy to understand language. Range of information adequate for general aquatic applications. Thank you Approved: 11/28/2012
Author seems knowledgeable. Approved: 10/29/2012
Needed pics together with written word Approved: 8/24/2012
LEDs will possibly be the only lights in the future. I feel most aquarium keepers would like real facts in choosing the correct LEDs for their tanks. Marine Depot sells alot of different LEDs, but no one, including manufactures, seems to want to help us make educated decisions on which one is needed. Thanks for all you do. Approved: 7/14/2012
A very good article,but I have only one question.I am using LED lighting over a nano tank.With all the number of LED lights I am using, what is the equation I use to find the total wattage of the LEDs. It is hard to get an answer as to what wattage LEDs are in their right. How do I get the wattage or what they colectively represent, of the LEDs over my tank? Brightness,lummns whatever.What wattage bulb do I have over my tank? Yours,Fishymon Approved: 4/26/2012
I was looking for the pros and cons of *not* metal halide reef lighting. This article was well written, but it covered everything I already knew, up to the point where I hoped to learn something. :- ) Approved: 3/18/2012
very!!!!!!!!!!!!!!!!!!!......informative love it!! Approved: 1/29/2012
was very specific and down to yhe point without being complicated Approved: 1/13/2012
where can I buy a external blue LED strip lights? EDITORS NOTE: Contact us at for help in locating LED strips. Approved: 11/6/2011
Great info. Thought I only had one question but read everything. Very helpful Approved: 9/23/2011
Nothing about the newer LED sets for live FW Plants or corals. Approved: 9/14/2011
I just started a salt water aquarium 2 months ago, and I want to add more sea life, but was very confused on the type of lighting to get. Now, I have a much better idea on how I should shop for lighting and sea life. Thanks. Approved: 8/30/2011
great bit of info Approved: 8/27/2011
More infor on the gain or loss (difference) between the bulbs would be nice. Ex the MH are HOT !!! and the PCs not so much. Light intencity between them would be nice. ex a 36" PC 10k vs a 36" T5 10K. Approved: 6/9/2011
Its been an pleasure to find this site and help me plan my marine tank, the only lighting guide that help a novice explain what to do thank you very much Approved: 4/29/2011
Answered a lot of the questions I initially had, in a common easy to understand way. Great Job Approved: 3/30/2011
It would be nice if you would instruct on how to properly calculate the correct bulbs or amount of lighting necessary. Is ther a formula? Like at 3 watts per gallon in a 65 gallon tank, I need 195 watts for a planted fresh water aquarium. If the tank is 24" deep & 3 long what & how many bulbs do I need. Well if I use 250 watt bulbs as stated above & my lighting system takes 4 bulbs, isnt that too much light? EDITORS NOTE...there is no "rule of thumb" of watts per gallon in lighting a reef tank. One watt of metal halide is not the same as one watt of flo. lighting is not the same as one watt of LED lighting. Send us an email ( and we can make some recommendations for you:-). Approved: 2/19/2011
Plenty of info for the beginner thats easy to understand. Many thanks Approved: 1/30/2011
Even though you mentioned length of lights on, I am trying to find out how long HQI, should be on, and the 420/460 and LED lights? Same time, different time? Can you help me? EDITORS NOTE: Please send an email to for assistance Approved: 8/31/2010
the only company that explained my problem. and i have had salt and freash water for ten years. Approved: 8/9/2010
great info Approved: 5/19/2010
very good Approved: 5/19/2010
GREAT INFO! Approved: 3/22/2010
Told me everything Approved: 1/20/2010
I have recd the information that I want Approved: 1/17/2010
great guide for lighting but i agree with posts : 3/15/09 and 3/9/09 needs to be "finished". Approved: 12/29/2009
Answered all the questions I have in one article--perfect! Approved: 12/23/2009
Good general article. Ansewered questions I did not know. Related articles would have been helpful. (glass top or open top, distance above.) Approved: 11/24/2009
This gave me the information I was looking for without being too technical. You could add some links for more technical information. Approved: 10/8/2009
You guys get pretty tec. This is the first article that breaks it down to power cost. Good job, I learned a lot. Approved: 8/10/2009
Tons of information about lighting from types to cost. Perfect. Approved: 8/5/2009
do i need another light with a m/h Approved: 3/29/2009
I can understand the types of light Approved: 3/28/2009
porque ahora ya se que tipo de luz pudo tener en mi acuario (Because Now I know what type of light I can have for my aquarium) Approved: 3/16/2009
Good start, however a few crucial factors.. such as explaining lumens (light measurement) and how it diminishes as distance grows (vital for healthy coral growth). About light requirments of fish.. it was left out there it doesnt really matter. I disagree.. fish are the same as humans, deprive them of light and things start to happen.. fish rot/bedsores ect, ect. Approved: 3/15/2009
Thank You,This helped alot on making my decision. Approved: 3/12/2009
great information! thanks alot! :) Approved: 3/11/2009
thanks thats great Approved: 3/11/2009
A good informative start, where to go to next to get to lighting 201? Approved: 3/9/2009
very helpful1 Approved: 2/28/2009
Good, but general. Needs more details such as what spectrum of light would go well with a certain fish or substrate. Approved: 2/24/2009
I am slowly learning about the marine tank and this helped me decide what lighting was best for my tank. Approved: 2/22/2009
Very informative Approved: 1/24/2009
Very good but needed more information on color spectrum. Approved: 1/11/2009
easy to read and understand, good basic info. Approved: 1/3/2009
They content was written for the layman and for people with some experience starting up an aquarium. It was easy to understand without going into a lot of depth on the different light spectrums. Thanks. It was very helpful.I would have liked more info on using 2 different spectrum lights to simulate the ocean. Dallas, TX Approved: 10/21/2008
I wish you would have mentioned distance with halides to surface of water. this is a 210 gallon reef and fish hard and soft coral. My come with end mounting arms about 4 or 5 inches above and I have heard 6 to 12" above give the halide a wider specturm and less heat what is your ideas. Thanks in advance. Ron Approved: 9/27/2008
Good article, but I expected more on understanding the pieces and parts needed for the different lighting schemes. Ex., for MH, what are the components that make up the system? In addition, I think you do have related articles, but none show up. Approved: 9/27/2008
simply thanks guys! Approved: 5/16/2008
Good information. Answers questions I did not know. Approved: 4/7/2008
great info keep the info coming thanks !! the more the better !!! Approved: 4/5/2008
It helped some but I would have liked more details. Lighting is the most confusing aspect of this hobby. Approved: 12/21/2007
Information is right down the middle; unfortunately, few tanks run right down the middle due to various economical or physical constraints. For example, reading Luis comment about which was better, there was no mention of the practicality of putting 200 watts of flourescent on a common beginners 55 gallon tank (3.64 watt/gal.) using NOs. At 40 watts/bulb, thats 5 bulbs, with only 12 inches of tank width, less if you still want to get food inbetween somewhere. So VHOs are probably a more practical bet, which I easily fit 4 - 55 watt bulbs for 220 watts, or 4 watts/gallon. However, the real question I would like answered is how to select bulbs - I can get 5400K, 6700K, 7800K, 10,000K, bright blue, deep blue/actinic, and 50/50 combos with 10,000K and actinic. So, for my 4 VHO 55 watt bulbs, or anyones flourescent only setup, what would your bulb combination recommendations be? And how long to run each bulb style/day? I saw one person reply to a similar article that they found 5400K Approved: 11/30/2007
A good article but I would have gone into more detail. For instance which is better or brighter between T5 and power compacts and VHO. Maybe in a letter article. Keep up the good work. Luis Approved: 8/24/2007
Article Details
Created on 8/24/2007.
Last Modified on 8/24/2007.
Last Modified by Dot Yuson.
Article has been viewed 53249 times.
Rated 8 out of 10 based on 206 votes.
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