Light fixture recommendation for a 75g tank - The Planted Tank Forum

 
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post #1 of 8 (permalink) Old 04-04-2013, 02:05 AM Thread Starter
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Light fixture recommendation for a 75g tank

Could someone recommend a good light fixture for a 75g tank? Planted, of course.

I've got a single bulb 48" fixture with some sort of "plant bulb" right now. I did have an Aqueon T5 48" light fixture as well, but it just died a little while ago. This is the second time I've had this problem and I WILL not be purchasing another one. The first time I contacted Aqueon and they replaced it free of charge, saying the fixture overheated/charged the bulb (or something like that, I no longer have the email), but that this would be the only replacement. Next time (i.e. NOW) I would have to buy the replacement.

I'm not sure what fixture to get though, that I can find at Pet smart/co or online. The ones I've seen have legs or clamps, which means either my cats can knock it over, or I'd have to remove the glass tops on the tank to install the fixture, leaving the tank open for cat attack. Can't suspend from ceiling either, because of cat attack.

Any suggestions? NO Aqueon, obviously.
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post #2 of 8 (permalink) Old 04-04-2013, 03:42 AM
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A 75 gallon tank is about 21 inches high, so the light would be about 18 inches from the substrate. The tank is about 18 inches front to back depth, so a single light may not adequately cover the whole tank unless the light is suspended a foot or more above the top of the tank. With the light sitting on top of the tank a Coralife or FishNeedIt 2 bulb T5HO light would give you low light, and it would take two of them, separated by about 10 inches to get uniform lighting over the whole tank. A Catalina two bulb T5HO light, in a extra wide housing, so the bulbs are about 7-8 inches apart would give you hight light if it sits on top of the tank, or medium light if it is suspended about 25 inches from the substrate, or low light if it is suspended about 30 inches from the substrate.

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post #3 of 8 (permalink) Old 04-05-2013, 04:28 AM Thread Starter
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Hmm..the Catalina brand appears to be quite expensive, however I've heard of people using regular shop lighting from Home Depot successfully?

I looked online and didn't see a single bulb with reflector for sale, to perhaps purchase two and put some space between them on top of the tank. Maybe if I go in person I'll see something.

However, I did find this:

http://www.homedepot.com/p/t/2029681...5#.UV5PZFcZ6i1

four bulbs, but they're t8. I saw some daylight 32w t8 bulbs on the site. Forgive me, I'm such a novice when it comes to lighting. If I set this on top of my tank, using all four bulbs, what sort of lighting would that be?

Or if I stick with t5 54w daylight bulbs, there's this, though I'm thinking I'd only want to use two, maybe, three bulbs, to avoid excessive algae growth.

http://www.homedepot.com/p/t/2030128...N#.UV5QVVcZ6i0

Before you ask, no, I am not currently introducing CO2 to this tank. I was, but misjudged the amount left in the tank and lost my fish when the regulator dumped the remaining CO2. I don't care for that regulator anyway, as I could never set it up on a timer because I had to readjust the bubble rate every time I turned it on.
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post #4 of 8 (permalink) Old 04-05-2013, 04:41 AM
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come to the new age and get ray2
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post #5 of 8 (permalink) Old 04-05-2013, 04:52 AM
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Re: Light fixture recommendation for a 75g tank

Mid-range LEDs still have an issue with light spread. The light is great right under the fixture but 6" off center and you lose a lot.

Most obvious with fixture right on top of the tank and with floaters or taller plants.




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post #6 of 8 (permalink) Old 04-05-2013, 12:22 PM
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[QUOTE=OVT;3039802]Mid-range LEDs still have an issue with light spread. The light is great right under the fixture but 6" off center and you lose a lot.

Most obvious with fixture right on top of the tank and with floaters or taller plants.



18" above substrate: -15% at 6", -23% at 9"
I suppose it depends on your definition of "a lot."
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post #7 of 8 (permalink) Old 04-05-2013, 02:57 PM
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Re: Light fixture recommendation for a 75g tank

If you can grow carpeting plants of your choice against the front glass @ 56 PAR, then you are done.

The Finnex PAR chart assumes that the light is going through empty water, not bouncing off floaters or taller plants 4" from the light. I like the charts but I also think and use my experience. I did test 2 Finnex Ray 2s before I made my comment.

Reading Hoppy's comments at post #2 is educational, at least he has been there

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post #8 of 8 (permalink) Old 04-05-2013, 03:17 PM
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[QUOTE=OVT;3041770]If you can grow carpeting plants of your choice against the front glass @ 56 PAR, then you are done.

What is the recommended PAR for growing micro sword?
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