# Experienced Lighting question.



## Abb (Mar 7, 2009)

75G tank. 18wide, 18high, 48long

Okay so im going to build a hood for my tank, im a very good DIY-smart guy. All i need to know is how to keep cost down, and what kind of lighting i should do. 

Now i work with HOT8's All the time, i know they are very good for lighting up big areas etc. Now What im wondering is, should i use T8's, or should i use expensive t5's. Im not worried about energy, as any fishtank hogs up enough, why not add a bit more. But how effiecient is it to light with a T8 vs a CFL bulb vs a T5HO setup. 

I can get t8+ ballasts and t6+ ballasts and bulbs for half the price of what you would pay so keep that in mind. I know t5 bulbs and ballasts are expensive. And not sure the potensial of CFL bulbs, but i know they are used. 

I know alot of people rule of thumb w/gallon. But its not a very good way to actually measure w/gallon because different tanks = different dimensions. So another question i ask, is how directional should light be, should you measure lumans instead of watt's per gallon? Because that is actual light output. Not watt's. Altho they seem to go higher hand in hand, watts = lumans. Its not always the case. 

I want to build a 48inch by 10inch hood. I would like about 2w p/gallon if you wanna say, at least.

My ultamate question is how many bulbs, and or what kind should i use!  If i could put in 4 HO T8 bulbs it would only all together cost me about 50 bucks.
My goal is to do this under 80$

Hope some1 has the answer!!! or can help


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## Mr Fishies (Sep 21, 2007)

There is no T5HO data in it, but the sticky at the top of the equipment forum will answer some of your comparison questions: Lighting Guide - Lumens/sq in vs. WPG. Sounds like you ruled out T5 anyways.

Despite the fact you don't like WPG, you want a WPG answer... So, you kind of answer your own question, 4 x T8HO = 176W right? 176/75 = 2.34666 WPG. It will fit in 10 inches no? You get them for $50 which leaves your cabinet to build, if you can do that for $30, problem solved.

You're not concerned about energy use, so I'm surprised you mention efficiency... If you want efficient, directional light, with any bulb, then you will need reflectors. A flat mylar reflector is cheap, but you bounce light right back down into the light that shot it in the first place.

You want directional reflectors, designed to maximize light bounced into the tank, even for T8, I bet your $80 goal is shot then. I'd bet 4 good T8 reflectors are >10" anyway. Could fit 3 maybe, since good reflectors can double your light, so you're still better off...but not for $80.

IMO, your project has conflicting specifications, small space, high efficiency, low cost...if you figure out how to cross all 3 off the list equally well, you should market it. Or figure out which requirement gets slid off the table into the bin.


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## ameekplec. (May 1, 2008)

It would depend on what the PAR of the T8 bulbs are. I'm not familiar with their outputs are, but with T5HO for a 75g, you could probably get away with 2 T5HO bulbs with decent reflectors. The reflectors are key, as is active cooling (cheap CPU fans are great for this).


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## Abb (Mar 7, 2009)

Mr Fishies
The only reasons it will be cheap is because i have alot of stuff sitting around where i work. Using T8 bulbs and ballasts i already have and will save alot of money. But Yes i will be making the actuall hood VERY efficient. Thats the upside is i have alot of material and know how to do that part of it. Just not the science of bulbs. Not sure if i should be more worried about lumens or wattage. What do the plants REALLY want? Because there are 20watt bulbs with 4000 lumens and 40 watt bulbs with 4000 lumens.


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## Mr Fishies (Sep 21, 2007)

Now, you've gone and done it, that's another variable to consider, sort of...

What we really want to measure is PAR (Photosynthetically active radiation), you can have a really bright light that is in a spectrum that is no good for plants (ie: Marine Actinic bulbs).

That requires a special meter ($300ish) or you buy bulbs that are known/measured to give the right spectrum...but most of us have to settle for buying lights in the 6500K spectrum and going for as many lumens as possible. So, from a practical standpoint, assuming you have a good spectrum light, more lumens = more light = more photosynthesis.


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## Abb (Mar 7, 2009)

Thats what im talking about. haha. Thanks for the good information. So if i can get some good T8's or some nice CFL lights, with the right spectrum and high lumon, it should work. Awsome news! That would keep the cost down. Theres also retrofit kits out there so im looking into that


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## bae (May 11, 2007)

Aquatic plants can use a wide range of frequencies, so get what looks good to you. A lot of people here like the 'daylight' type color temperature, more toward the blue end of the spectrum, but you can get excellent growth from cool whites which are technically more or less green (althought they don't look it to our eyes). There are also 'sunlight' or 'sunshine' color temperature lights that look good to my eye and are commodity items, at least in T12. They probably have them in T8 by now. Avoid the purple-pink gro-lux type -- they look ugly and don't promote plant growth all that well. And the various 'vitalite' types that are supposed to closely mimic sunlight at a high price aren't actually all that much better than cool whites or your choice of standard commodity tube for plant growth.

Note that fluorescents produce less light over time. If you're really serious, T12s should be changed every 6-12 months. T8s are alleged to last substantially longer without losing much luminosity. If growth slacks off or plants start stretching toward the light, or you notice dark rings at the ends of the tubes, it's probably time to change them. Just like the reasonably priced printer that bankrupts you buying toner, you have to consider the cost of consumables.

The thing with lumens is that they are defined as brightness to the human eye. Your eyes don't perceive all wavelengths equally. So lumens aren't necessarily a good metric of usable light output per watt for purposes other than lighting for people.


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