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Discussion Starter #1
I am planning a low light non-co2 tank, dimensions are 150cm L x 60cm H x 50cm H, which is about 120 Gallons. I would like to use Coralife T5 28w 6,700K and Colormax.

I want to achieve about 1.5w to 2w per gallon. Now as I know this wattage is used for T8 which are about 36-38w bulbs, how many T5s can I use to achieve 1.5-2wpg?

Is there a site to see how many watts of T5 is equivelant to how many watts of T8s?

I would appreciate any help.

Thanks.
 

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They are Equal watt for watt. Its just that T5 fixtures normally have much better reflectors.
I disagree. According to everything that I have read the smaller the diameter bulb the more light it puts out for a given wattage (i.e. T-8 is better than T-12). While reflectors can be a very important part of getting light to the plants, all things being equal a T-5 bulb will be better than a T-8.
 

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Agreed that T5 are more intense then T8s. And even better with reflectors in getting the light in.

So according to SpeedEuphoria the wattage is the same. That means for me to get about 1.8wpg I would need 8 bulbs of 28 watts.

Thanks for your help.
 

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For the OP, the WPG rule was thought up using T12 bulbs not T8.

Heres some info and my opinnions:
This one doesn't mention T5 only CF
http://woo.gotdns.com/Aquarium/Lighting.htm

This one talks about them all and how T5 HO loses efficiency compared to T8 and regular T5
http://ecmweb.com/ops/electric_fluorescent_lamp_coming/

Theres many other places that you can search and find that the lumens/par/ect.. is relatively the same for T5/PC/T8 watt for watt if you take the reflector out of the equation. The difference is the reflectors. Smaller T5's allow less restrike and room for better reflectors. Hence why people believe that T5 is better than PC, all in the reflector. Reflectors are important as far as efficiency, for instance 1/2 the bulb is facing the water and the other 1/2 is wasted w/o a reflector(just for conversation), so from a perfect reflector you stand to gain 50% of the light that you would be losing.

But in the end the ballast is driving the bulb, and you will find that the normal ballast factor for T8 ballasts is ~.88 where the T5 ballasts have ~1.0 ballast factor meaning that you getting 100% of the watts claimed delivered to the light. So when you figure this then you actually getting less watts delivered to a normal T8 setup due to the ballast.

Then again there is ODNO
 
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