# Lighting Requirements



## koontzman (Nov 9, 2009)

I have this 120 gallon tank. I would like to set up as a planted freshwater.

Instead of $100's, what if I got a couple of 4 foot 40 watt bulbs from Home Depot like you see on any average ceiling? 

I heard ~4 watts/gallon = ~500 watts needed. And I heard ~10,000-15,000 lumens (?)

But, if I left the lights on for 14 hours a day (like normal daylight) would that be enough to keep the plants alive?


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## Mr Fishies (Sep 21, 2007)

A little more information will help:

Is it a 120 High (48") or Long (60)"? Depth of your tank beyond 18-20 inches makes a difference.

What kind of plants do you want to keep? Some plants require more light than others to survive/thrive/reds to colour up etc (if that's your goal)


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## koontzman (Nov 9, 2009)

thanks for answering. 

well, apparently it's a custom job, because it is 50" long, by 27" high, by 23". It has gold tinted mirror which extends a further 8" up (making it a total of 33" high, but I can't use all that due to these glass bulkheads inside)

I like the displays which look like Amazon streams. Some of the plants I think are the Amazon sword. I like cryptocoryne's, grass lke plants like vallisneria. I haven't grown anything with red in it yet, as I didn't want to add chemicals for the iron requirements.

I'm thinking now that the fish will be schools of different tetras. I think Glowlight Tetra's look good in low light. 

I would like Tetra's that school very well, I like the group action around rocks etc.


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## Darkblade48 (Jan 28, 2008)

koontzman said:


> I have this 120 gallon tank. I would like to set up as a planted freshwater.
> 
> I heard ~4 watts/gallon = ~500 watts needed. And I heard ~10,000-15,000 lumens (?)
> 
> But, if I left the lights on for 14 hours a day (like normal daylight) would that be enough to keep the plants alive?


This would be more than enough light for your plants; in fact with that much light, I would be afraid of starting an algae farm instead.

You will probably only need 8-10 hours of light maximum.

In addition, depending on what kind of bulbs you use will determine how much total light you will have (i.e. T12 bulbs are less efficient than T8 bulbs).

Finally, regardless, with that much lighting you will need to look at CO2 as well as fertilization (i.e. both macro and micronutrients).


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## bae (May 11, 2007)

This is an interesting problem. Deep tanks are not only hard to work in, but they need intense light since so much gets absorbed on the way down, in addition to the inverse square rule about dispersion of light over distance -- twice as far means 1/4 the intensity.

I'd recommend you go for 4 T8 tubes as minimum lighting. T8's are beginning to replace the usual shoplight T12s, so the fixtures and tubes are almost as easy to find. T8s are more efficient than T12s in producing light -- you get more light per watt. 

I've got a 4 tube T8 fixture here that I picked up some years ago when someone was throwing it out. It needs a power cord, and I have no idea if it works, but if you want to try it, I'll loan it to you.

You might try using a lot of driftwood in the tank, with anubias, java fern and mosses attached to the upper parts of the wood. You may be able to get a reasonable stand of jungle vallisneria if you start with several large plants -- its leaves are very long (4-5') and grow up and float on the water surface, so they are getting most of their light there. You could use other floating plants as well. I don't think you'll have much luck growing plants in the bottom of the tank without really intense light -- e.g. metal halides which are big bucks, big energy use and run very hot.

I think a lot of driftwood with roots dangling down from floating plants, and schools of brightly colored tetras flitting through them would look like a window into a rainforest stream. Amazon swords are actually mostly from areas south of the Amazon and as far north as Texas, and they are normally only under water in the rainy season. Most forest streams don't have much in the way of rooted aquatic plants at all.

Another possibility is setting up the tank only part full, with terrestrial plants growing from the walls or on wood emerging from the tank. You can attach cork bark to the walls, or make up a panel of coarse coconut fibre and grow the plants on it.


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## Calmer (Mar 9, 2008)

With the aquarium 50 inches long you may need to hang the 48" lights securely from the ceiling to take the weight. Or build a wooden canopy for it and mount the light fixtures inside.


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## koontzman (Nov 9, 2009)

Thanks for all that good info. I read on Wikipedia that t8 has a "nominal wattage" of 15w whereas the t12 is 125 watts. http://en.wikipedia.org/wiki/Fluorescent_lamp (near the bottom). t8's are more efficient than t12's, but isn't it better to have all that wattage?

That's very kind of you to offer to let me give your lights a go. I'm going to replace the silicone, and then give it a test, and then I may take you up on that. I've got a line on a light from Craigs' List. Lots there actually.


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## Darkblade48 (Jan 28, 2008)

koontzman said:


> Thanks for all that good info. I read on Wikipedia that t8 has a "nominal wattage" of 15w whereas the t12 is 125 watts. http://en.wikipedia.org/wiki/Fluorescent_lamp (near the bottom). t8's are more efficient than t12's, but isn't it better to have all that wattage?


Not sure where you got 125 watts for the T12 bulbs for but...

Wattage is not the same as the amount of light that is being outputted. Wattage simply means how much power the light is consuming to output a certain amount of light. T8 bulbs use less energy to output the same amount of light as a T12 bulb. Thus, if you wanted to keep the wattage (the power consumed) the same, (say) x watts of T8 bulbs would output more light than x watts of T12 bulbs.


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## koontzman (Nov 9, 2009)

*watt power*



Darkblade48 said:


> Not sure where you got 125 watts for the T12 bulbs for but...
> 
> Wattage is not the same as the amount of light that is being outputted.


yes, right. It's to do with lumins, right. That is another read for me to get onto, and all those conversions to figure out.


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## bae (May 11, 2007)

koontzman said:


> yes, right. It's to do with lumins, right. That is another read for me to get onto, and all those conversions to figure out.


Lumens are a measure of how bright it looks to the human eye. If you want to get all scientific and analytical, what you want is PAR, photosynthetically active radiation, which you can measure with a PAR meter. Neither plants nor the eye use all wavelengths equally, and many aquatic plants have adaptations to utilize wavelengths outside the PAR definition.

Efficency is a measure of how much of the electricity consumed goes into light vs heat. A T8 fixture gives more light and less heat for the same amount of electricity than a T12 fixture.

Unless you enjoy trying to figure out all this in advance, and then have it run into the fact that biological systems are a lot more complicated and less predictable than one might hope, I suggest you start with something reasonable, like 4 T8 tubes, and some undemanding plants, and attaching plants like Anubias, java fern and mosses higher in the tank, or going for floating plants.

If you go for the kind of lighting that will grow high light plants almost 3 feet from the light, it's going to take a lot of power and generate a lot of heat.


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## koontzman (Nov 9, 2009)

That sounds like good advice. A guy up at Lucky's said that a 15,000 lumen light, 48" for $100 (tax incl.) would satisfy my planned set up of a planted tank with Tetra type fish. Does that sound right, or would that be with plants higher up in the tank as with 4 T8's?


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## Darkblade48 (Jan 28, 2008)

As bae mentioned, the best measurement is PAR and not lumens.

Also, that price seems outrageous for a light fixture, unless it is a T5HO fixture or something of the like. You could probably get a 48" T8 fixture for much cheaper from the hardware store.


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## Plaid (Nov 10, 2008)

I'm gonna come out of my prolonged lurking spell to help out here. This forum sends you an email on your birthday, so I'm hanging around for a while.

For what you want to grow (Crypts, Swords, other low-medium light plants), you can probably get away with much less than 4 watts per gallon. The WPG rule falls apart completely on large or small tanks, and is just a guideline anyway. With 1-2 watts per gallon on that tank, you can grow whatever you want. It just becomes an issue of CO2 and nutrient balance. You should probably stick to 1 watt per gallon, to be honest.

You should also throw the concept of "Lumens" out the window. The Lumen is an SI unit based on how bright light looks to the human eye. Plants don't care at all how it looks to us, it's about how it looks to then. Light for plants is measured in PAR, as Darkblade mentioned. Follow all his advice. He won't say so, but he's one of the best.

Read anything by Tom Barr. He has a forum which is dedicated to plants. He is one of the best in the business.

Here's a link to a 1.5 wpg, 75g tank. He's got his CO2 running well, and this proves that high lighting is redundant, and merely promotes algal growth.

http://media.photobucket.com/image/low light carpet tank/plantbrain/resized70galADAwith1.5wgal.jpg

If direct linking isn't allowed, just assume that the tank is sexy. Dead sexy.

Good luck,
Wes


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## bae (May 11, 2007)

Darkblade48 said:


> Also, that price seems outrageous for a light fixture, unless it is a T5HO fixture or something of the like. You could probably get a 48" T8 fixture for much cheaper from the hardware store.


You also have to take into account the cost of replacement tubes. T12s are a commodity item and are dead cheap. T8s these days are almost as cheap. T5s and various HOs and other specialty types can be big bucks because they are made for a small market compared to general lighting types like T12s and T8s.

It can be worse than printers -- the printer is cheap but the consumables are outrageous.

I'm beyond my own expertise when it comes to wide, deep tanks. Either experiment or consult a planted tank specialty forum. If you want to experiment, my thrifty soul says start with something cheap. And the offer to borrow my 4-tube T8 fixture stands.

http://www.plantedtank.net/forums/lighting/ might be a good place to find specialized expertise.


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## koontzman (Nov 9, 2009)

oh, that is a very good sited at plantedtank.net. I joined that forum as well.


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