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Hi all, just bought a new light for my aquarium. Really happy with the result. I have 1 x 40watt tube and 1 x 36watt 10,000k tube. Whilst I was shopping around I noticed these T5 & T8 tubes. What does that mean???

Thanks for your help in advance
Cheers
Crusha

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Those who say they cant, Never will !!!

Hi,
The "Ts" tell you what diameter the bulbs are.
T-12= 1 1/2 inch - 12 eighths of an inch in diameter
T-8 = 1 inch - 8 eighths of an inch in diameter
T-5 = 5/8 inch - 5 eighths of an inch in diameter

Other values to look at are:
CRI - Color Rendering Index
This is a measure of how true colors look under this
bulb. A CRI over 70 is considered good and anything over
85 will be very good. In other words reds look red
and greens look green without any washing out.

The apparent whiteness of a bulb is given as degrees
Kelvin (K). This describes what a solid black iron ball
looks like as it is heated. At low temperature it turns
shades of red and as the temperature increases, it shifts
through the spectrum to yellow to white and to blue.
Each shift is higher temperature and a higher Kelvin
rating.
Most incandescent bulbs fall between 2700-3000K.
Fluorescents run between 4000K and range to 20,000K

The thing is that fluorescents in the 4000-5000K range
tend to make aquariums appear yellowish or weakly lit.
Bulbs over 10,000K start to make things washed out in
an aquarium. Most who run bulbs in the 10,000 and 20,000K
range also include bulbs in the 6700K range to "mellow out"
the light.
Over all, bulbs in the 6700-8800K range give the best
CRI and are best for both plants and fish.

Saltwater tanks with invertebrates, require the 20,000K
light.

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

The other differance between the two is light output, heat, and energy consumption. There is a slightly higher lumen output by the T5 bulb and it uses less power while generating a lot less heat. There light output is roughly three times that of a conventional T12 bulb. The T5's are nice because you can stack more next to eachother and generate a lot less heat.

Thanks for your replies, that helps a lot.

I had two "white" tubes to start with, dont know what they were only had 36 watts marked on tube (came with the reflector) but they made the tank look really green. When I swapped 1 for the 10,000k it looked much, much better.

Cheers
Crusha

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Those who say they cant, Never will !!!

How big is your tank? Is the other bulb just a plain bulb or is it a 6500k bulb?

Your welcome

Mrwizerd, I have a 48 x 18 x 13 aquarium. The tube I got with the unit doesn't have anything on it except 40 watts, no "k" units on it or the box. It is white when I turn it on whereas the new tube I got (10,000) is pink.

The new tube has counteracted the greenish tinge that the two 40 watt tubes made. I might go and buy a 6500K anyway, they aren't that expensive at the hardware shop.

The LFS said the tubes included were for plant growth so i'm assuming they are 6500. But then again, who knows??

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Those who say they cant, Never will !!!

Hi,
The "white" lights were primarily designed for reading
and in places where folks were using their eyes alot.
They are called "warm" or "cool" white and lack the
harsh headache causing glare of sunlight.

The DAYLIGHT or SUNLIGHT labeled bulbs are the best for
plants and are generally around 6700K.

Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

Thanx for that info Frank. I could only find 6500 tubes. I am going to try one of those and see what effect it has on things.

Cheers
Crusha

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Those who say they cant, Never will !!!

Also worth noting that T8 and T5 have much higher usable light output than T12. If you would like to delve deeper, here]http://woo.gotdns.com/Aquarium/Lighting.htm[/link] is a good page discussing it. [link=Here is my Excel compatible spreadsheet where you can compare to "Equiv T12 wpg" derived from lumens/watt (see bulbs book), amongst other things.

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http://justanothertank.com

Now the next question might be are they interchangeable? Say i have T8's and want to swap in something else (excluding size issues - with a bit of modification anything will fit )

T8 T10 T 12 and normal output T5's use the same ballast type though T5's require an adapter to make the gs fit. Hight Output T5's require a different ballast. T8's have a little less light output in lumen's then the T5's the main benefit is power saving, unless your talking about HOT5's

At 48", T5 is 24w and T8 is 32w (T12 is 40w). Total lumen output between T5 and T8 isn't enough to worry about. Wiser would be to overdrive your T8 fixture.

T8 and T10 will fire from most T12 electronic start ballasts. I am under the impression T6 will as well, but have not tried it. I was under the impression T5 and T5HO were not backwards compatible.

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http://justanothertank.com