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Discussion Starter · #1 ·
I've got a 20g long tank (30") with a 24" 48w T5-HO fixture suspended 12" above it with 2 pieces of window screening in it to reduce the light level. Is it detrimental to have a light fixture that's shorter than the length of the tank itself, or is it fine as long as it's suspended? Thanks!
 

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Your Lighting Question

Good morning fre...

Just plant low light plants in the ends where the light doesn't cover. That's the way nature does it. I have a 38 G tank with a short bulb. The tank just came that way. So, I have Anubias, Crypts and Java fern in those areas that don't get much light and the plants that require more light in the areas in between.

The tank looks fine and the plants grow very well. Don't forget to change out half the water weekly and dose a good fert too. The health of your fish and plants depend on weekly water changes of at least 50 percent.

Above everything else, have fun!

B
 

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Discussion Starter · #3 ·
Makes sense. I was thinking about just replacing the short fixture with a 30" Dual T5 Coralife Aqualight (fw, of course) strip light since it has true length bulbs and I could just sit it right on top of the tank...thoughts? I need something that's gonna grow HC good but not TOO much light and I'm thinking this might be just about right...
 

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Your Light Fixture Question

Hello again fre...

It's been a long time since I've had a small tank. Correct me if I'm wrong, but a 20 G long is only 12 inches tall, so my call is a T5 would be pretty intense, but distribute the light over a small area. If you have a strip that will accomodate two bulbs, then a couple of 6500 K, T8s from the local hardware store would likely suffice.

This is just an option, I'm strictly low tech, low light. I like to keep this hobby simple and inexpensive.

B
 

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More Lighting Info

I thought T5NO (not HO) was more or less equivalent to a T8?
freph...

The T5 Nominal Output may have a similar intensity, but won't distribute the light over as large an area of the bottom of the tank as the T8. I'm not familiar with the specs of the T5 bulb, I've never used them. I do have the T8s and 12s in my tanks.

B
 

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Discussion Starter · #7 ·
Anyone care to chime in on this? I'd still like lighting high enough for my HC to grow healthily and it's easier to find dual T5NO fixtures than dual T8 fixtures as far as I can tell from searching....

T5NO vs T8 differences?
 

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I suspect the 6" on either end are as well lit as the front and back of the tank. Your fixture doesn't fit from front to back and it is fine, right? Since you already have it try it. Maybe you could take photos and play with the exposure to see if it really is that much dimmer at the ends.

Switching to T8 or T5NO would put you at medium light with the fixture on the top of the tank, same as the T5 at 12" over the tank. See the chart here.
http://www.plantedtank.net/forums/lighting/105774-par-vs-distance-t5-t12-pc.html
 

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The 3" gap per side is not going to hurt you because your side glass will reflect back some of the light unless you hae painted it or a back drop is tuck to them.

The PAR value of the gap is going to be similar to the edge of the light.
 

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I have three 20g longs set up, all have 2x18W T5NO's sitting directly on the tank. I think it's plenty of light on a 13" tank. Below is a (bad) pic of the older tank, which is my Q/holding tank:

 
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